SOME PEOPLE on the Eastern Shore are worried about James Michener's new novel, "Chesapeake": They're afraid it will bring hordes of new people across the bridge to snoop around and build hotdog stands and change everything.

Some people on the Eastern Shore are always worried. In 1968 they worried about what would happen after what one man called "the insurrection" of blacks in Cambridge. In 1952 they worried about the Bay Bridge and how tourists would overrun the place. And before that, they worried about the railroad.

Changes do come to the Eastern Shore, but slowly. sometimes you only notice them long after they've happened.

The land itself has brought changes. In Colonial days it was planted in tobacco, but farmers discovered that tomatoes, melons and other fruits and vegetables were kinder to the soil.

"The trouble was, you had to have pickers, migrant labor," said Maryland State Sen. Frederick C. Malkus, "and this brought problems of its own. It's hard to work with seasonal labor. Also, California was taking over the tomato market. so a lot of the Eastern Shore people went to grain."

Grain meant mostly corn and soy beans, and with the grain came the poultry industry, making the Delmarva Peninsula practically the chicken capital of the world.

Drive down Route 50 past Easton, and you pass the biggest chicken house you ever saw, with a sign, "This building produces 375,000 broilers each year." And that's only one.

These changes, which have come since World War II, have brought others with them. Some towns that had depended utterly on melons or oysters had to reinvent themselves. Crisfield, at the southern tip of the Maryland Shore, used to be a seafood center. Today some of the fine old white houses lining its main street are vacant, and the marinas are not exactly crowded with boats, though there is always activity around the pier where the Tangier Island ferry docks.

Yet trucks bustle up and down the highway, and some new houses stand beside the old paintless ones.

"The biggest industry in Crisfield now is the Sherwin-Williams paintbrush plant," said Ralph O. Dulany, retired chairman of the state's Economic Development Advisory Committee and organizer of the Wisomico County Housing Authority.

Changes in employment brought changes in housing. "My wife began crusading 40 years ago for better housing for the migrant workers," Dulany said. "Our housing authority built nearly 400 units, mostly in Salisbury, and these have helped, and so have the government regulations on migrant housing. But there are still quite a few shacks that shouldn't be inhabited but are."

Some changes on the Eastern Shore can be traced to the very shape of the land. For one thing, as Malkus remarked, the rivers in the northern part are deeper, while south of the Choptank they tend to be shallow and surrounded by marshes. For another thing, there is the matter of waterfront. Which brings us to Talbot County.

"Queen Anne's County, for instance, has just one long river, but Talbot has 602 miles of waterfront," said Frank S. Dudley, a fourth-generation Shore man who runs a real-estate firm among other things."That's more than any other county in the nation. What it means is that you can have yourself a private shore without having to buy a huge amount of acreage."

Talbot is unique among the nine Maryland Shore counties. It is the social county, the rich county and the Shore's center. The name it prefers for itself is "the Colonial County," and the historical society map shows dozens of beautiful 18th-century mansions.

Down Morris Street in Oxford, alongside the Tred Avon River, you see one graceful old house after another, some of them pre-Revolutionary. Winding your way to St. Michaels with its harbor and back toward Easton, the county seat, you notice the signs of quiet wealth: the long, long hedge beyond which you can glimpse orchards and horse barns, the modest entrance flanked by brick pillars, the main house itself out of sight among the tall pines and oaks but fronted by acres of clipped lawn.

"Oh, there are duPonts all over the Eastern Shore," said Charlton (Burt) Gunter, who for 20 years owned Kingston Hall, one of the Shore's great showplaces, before retiring to Oxford. "The horsey ones have a great big place in the north end, but they have some farms around here, too."

DuPonts have been coming to the Eastern Shore from Wilmington for generations, and it was fashionable for rich northerners from Pittsburgh, Philadelphia and New York to buy farms or summer homes as early as the turn of the century, but the real influx of moneyed outsiders began in the 1940s and redoubled when the bridge opened a decade later.

The prices redoubled, too. A 1905 Easton Ledger article lists sales of various estates and historic homes for $12,000 to $15,000 and adds, "All of the above named farms are water fronts and therefore brought fancy prices. There are many inland farms in the county which brought figures around $10,000."

Today you can get a nice little five-acre place on the Wye River for $225,-000, or a very ordinary three-bedroom bungalow in "the St. Michaels area" for $53,500, or if you're serious about it, an 835-acre waterfront farm with 175 tillable acres and the rest in marshland, "excellent hunting," plus nine-room farmhouse for $750,000.

"Something else that brought money here was the hospital," Dudley said. With 260 beds, the Easton facility has drawn doctors from all over the East to live and work nearby. "The thing about Talbot County is that it attracts affluent people who have retired early but aren't ready to sit around and do nothing, so they have a lot of energy. One guy built the Tidewater Inn (a large, modern $1,600,000 hotel in Easton), just himself, no syndicate or anything, just to have something to do."

The new people have made their mark on Talbot County. You can spot them, chic in their L. L. Bean windbreakers and yachting sneakers, their elegantly rough clothes. Some are accepted more easily than others.

"I've seen 'em come in here and want to change things," commented one long-time resident. "They talk to everybody and have a lot of ideas and maybe they run for local office. Never can figure out why they're not elected. Other people are quiet about it and just seem to become part of the community. They say you're an outsider until no one can remember where your grandfather came from."

The clothes can fool you, by the way. The friendly graying guy who comes wobbling past on his bike and stays to chat as if he had all the time in the world turns out to be an investor and builder with projects all over the country.

Michener was one of the ones who blended in, Talbot people say. He had been coming to the Shore for years, rented a house near the St. Michaels Yacht Club, and two years ago bought a place in St. Michaels.

"He mixed with everybody," said Bill Benson, who for 36 years ran the ferry between Oxford and Bellevue. "By and large, I think the Shore accepted him very well. He had a lot of friends among the Talbot County set and also the old-timers. A likable man."

Benson was a good source for Michener, apparently, because the writer spent a lot of time chatting with him. One bit of history he passed on was the story of Sharps Island, in the mouth of the Choptank, which was washed away completely by the sea. In the book, a fictional island set in that very spot disappears in a storm.

"I haven't read the book yet," Benson added. "My wife's going through it first. I heard some people are trying to place this and that character or event, and what they're forgetting is that it's not a history. It's a novel and people shouldn't try to associate it with the real thing."

Benson had better get reading, or he'll find himself one of the few Shore people who hasn't at least tackled the long book. The publishers say it is seling better than any book in the history of the region.

Many residents, like Elizabeth Hall of Crisfield, report that they are in the middle of it. Some of these have reservations.

"I'm not so sure it rings true to the spirit of the people of the Eastern Shore," she said.

"To us natives of the lower Shore, it's not quite us, if you know what I mean. Also, I feel there's too much concentration on Talbot County."

Mrs. William H. Brown Jr., another long-time resident of the south end, is anxious to see the novel because she grew up in the Annapolis area and knows well the people who live near, or on, or by the water and its products.

Michener himself, just returned from a visit to South Africa and enjoying a few days in his place here, said the reason he has got along so well with the Shore is that "I take a lot of time. I've been here two years, and I keep a low profile. If I had come in as the glib hot-shot operator I would have met resistance."

Gradually, people invited the writer and his wife to parties, on hunting and fishing trips. "I moved at their speed," he said.

He also sought out the black community and found that "though emotionally this is part of the Old South, the more sensible people wanted to withdraw from that, they didn't want to go that way. Since the trouble in Cambridge there have been some social gains, not enormous, but significant."

Soon after the riots, he noted, St. Michaels elected a black mayor. A good sign, he thought.

Now that he has moved his books here, he is thinking about getting a boat.

"If you don't have a boat on the Shore, it's almost as bad as being a Democrat. I don't have a boat, and I'm a Democrat. So I walk very carefully, very carefully."

If there is a difference between Talbot County's open-armed reception of both the author and his book, and the caution that emanates from other counties, it may be because Talbot sees more outsiders, is more accustomed to tourists. Antique shops and pricey "Colonial" restaurants abound, and so many cars make the Easton-OxfordRoyal Oak circuit that the 218-year-old Tred Avon ferry runs almost nonstop in the summer.

(Speaking of which, Talbot may have a reputation of being more politically liberal and receptive to change than other counties, but the local worriers won't deny that they were upset when Benson retired. They needn't have fretted: The new ferryman, Gilbert Clark, comes from a family that has run ferries on Long Island for five generations.)

The other bayside counties don't see as many tourists, aside from the stream of cars heading for the ocean beaches every season. Even an Oxford resident can say that "this county is atypical as hell -- the real Eastern Shore is those little towns down the spine, Denton, Sudlersville, Centreville, Chestertown."

To places like these, the new highways have brought not tourists but displacement. As in hometowns all over the country, the small businesses on Main Street have been hit hard by giant shopping centers on the out-skirts. Supermarkets have taken away the cash customers and left the little family stores the dubious option of catering to drop-ins and credit-seekers.

Take Chestertown: a charming spot on the Chester River, founded in 1706, a place where George Washington stayed at least eight times (being on a main north-south route during the Revolution), with a row of dignified Colonial houses, pillared and gardened, overlooking the water and sycamores arching over the High Street with its grass-tufted brick sidewalks and white porches.

One block back from this cordial scene are paintless board houses, spavined and tumbledown. One feels the town is struggling hard: There is a college, old stores are being renovated, bright little shops give an air of bustle to the main drag. But the big shopping malls are outside, a mile or so away, the ones with the major chain stores and the limitless parking.

(It's still pretty countrified: At midday a deer bounds neatly across the highway, just missing an A&P truck, and vanishes into the woods.)

The jobs are elsewhere, too. A Campbell Soups plant runs buses to bring in its far-flung workers. Some people live in Chestertown and work in Dover or even Elkton, 46 miles away, commuting in car pools. They can still save money with the modest scale of life in Chestertown.

"Except for Salisbury and Cambridge," one old-timer said, "there's not that much of a push for industry. People don't want labor problems, so they look for non-union companies. They're very fussy about clean industry."

From a veteran observer of state affairs: "The Shore is a little like the Old South: The economy goes with the land. East and West Shores are so separate they have different treasuries. The Delmarva Regional Council does something to counter the fact that while the peninsula is geographically a unit it is in three different states. But the main thing that's going to end their isolation is the car. Sooner or later."

Perhaps the best way to understand how the Eastern Shore deals with change is to talk to Fred Malkus, a state senator since 1951, a native Marylander, conservative and proud of it. An expert turtle trapper, he took James Michener "turkling" to give the author first-hand experience for his book.

"Our area hasn't basically changed," said Malkus, sitting back in his padded chair in the small, book-lined office he keeps across from the courthouse in Cambridge. "The only real difference is the Ocean City traffic; we're loaded down with it. The population's gone up some, but not a whole lot."

Sharp eyes watched carefully from under the heavy brows. Even when they twinkled, they watched. But his laugh was a good [WORDS ILLEGIBLE] Every few minutes he took a phone call and gave advice about crops. Some cantaloupes were piled by the front door.

"The hunting and fishing are still the same, there's more geese than ever, and the deer population is bursting at the seams -- we got 1,700 here last year. Ducks are down some. Most of us here a long time don't want any big change. We'd like to see more small industries. The agriculture is healthy, though it has the usual ups and downs."

In 1900, he noted, the population of Prince Georges County was just 32 more souls than Dorchester County, where Cambridge is. Today Prince Georges has 650,000 people, Dorchester 30,000.

"Yet rural Maryland has a quarter of the state population and it's treated like a stepchild. We're not getting our fair share. Most state representatives don't really know what we're all about, what our needs are, and don't seem to care. Most of them are from the Washington area, they're johnny-come-late-lies."

He emphasized that though he was born in Baltimore, he has lived on the Shore -- in the same place -- since he was 3.

"Change? I don't see any big change," he said. He hasn't read the book either.But he means to.