BECAUSE IT'S so close to New York City, Fire Island has special appeal for New Yorkers. It's only a two-hour trip by train or car and ferry from Manhattan to a peaceful, seabound resort -- a sandbar and barrier island about 32 miles long and 200 yards to half a mile wide. Every year, winter storms in the Atlantic Ocean erode the beach by five or 10 feet. An island restauranteur remembers: "The dunes used to be 100 years beyond my porch. Now they're right underneath my restaurant."

In summer, about 25,000 residents and visitors crowd onto Fire Island every weekend, leaving their cars -- which are prohibited by law -- behind. The island has remained a secluded refuge for centuries. During Prohibition, rum runners found an entranceway to the marketplace via the Great South Bay, which separates Long Island from Fire Island. One homeowner in the community of Saltaire remembers: "Everyone brought their little red wagons to the ferry dock after dark to pick up the rum." Until the early 1980s a couple of the rum runners' boats still served in the ferry fleet, carrying passengers between Fire Island and the mainland.

Prohibition marked a turning point for Fire Island's once sedate image. The island began attracting an artistic and high-living cafe society crowd. Today some communities that have earned the entire island an undeserved, wild reputation coexist with quiet enclaves of family communities -- from the middle class in Ocean Beach to the upper middle class in Saltaire and the very wealthy and socially prominent in Point O" Woods.

By the 1960s, New York City politicians had their eyes on the commercial possibilities of Fire Island -- so near and yet so far from the madding crowd of Manhattan's busy streets. Fire Island still had no roads in the '60s -- only cement sidewalks. By law the only cars allowed on the island were police cars, fire trucks, buses and four-wheel drives specially licensed in winter and bicycles and grocery carts -- and no vehicle wider than the cement walks.

Politician Robert Moses wanted to build roads, dreaming that more people could reach the island. More businesses and houses would be required. Moses managed to effect a causeway between Long Island and the western tip of Fire Island, where a park and public beach are now named for him. But that's as near as cars get to Fire Island. Homeowners ran to meetings in mid-winter, in rough weather, to win the war against the roads.

What they preserved is a jewel of an island as sparkling as a Mediterranean coastal town. Fire Island looks like a fantasy kingdom, as you approach by boat on a sunny day. The houses on the flat island are tiny and quaint, whether clapboard or glistening white brick with picture windows overlooking the bay.

Few houses have more than one or two stories. Severe hurricanes, even sometimes simple thunderstorms, have toppled houses. In 1938, a hurricane reduced houses in Kismet and Saltaire, on the western end of the island, to rubble. Only in the '70s and '80s did "new money" arrive to build new houses, generally modern, wood-and-glass designs on Saltaire's beach, in contrast to the quaint shingle houses near the bay.

Fire Island has always had an exotic aura. Originally pirates found a haven on its beaches. Whale sighters used its shores for commercial purposes. The island may even have gotten its name from whalers summoning help from the mainland after they made a catch; they burned driftwood on the beaches. Now the only help wanted from the mainland is money to try to stave off further erosion. In 1964, the federal government bought the island and declared it national parkland under the aegis of the National Park Service. But so far, the island has attracted more visitors and homeowners than funds.

It's easy to get to and from Fire Island. You drive on the Long Island Expressway or the Southern State Parkway or take a train from the Long Island Railroad Station under Madison Square Garden to Bayshore, Sayville or Patchogue, Long Island. These towns serve as ferry ports for Fire Island. Several Long Island taxi and limousine firms, particularly Aadvark and Tommy's Taxi in Bayshore, Colonial in Sayville, and Mike's, Ernie's, George's, Blue Star, Main, Sandy's Taxi in Patchogue have direct service between Manhattan and the ferries.

Ferry schedules are coordinated with the trains. Taxis wait at trains and ferries to shuttle people back and forth. During weekend rush hours, the taxis get very crowded. Wear blue socks, if you want to keep track of your own feet enroute.

In Bayshore, ferries connect with Kismet, a singles community; Saltaire for families, with the community's own yacht club, for members only; Fair Harbor with singles and families coexisting quietly, many in communications jobs; Dunewood for families; Ocean Beach for families and singles who like the urban touches of having a post office, bank, pharmacy, movie theatre, varied restaurants, and the Fire Island newspaper office in the center of town.

Most other communities have only a grocery store, a restaurant or two, sometimes a liquor store and a mailbox. From Bayshore, too, you take ferries to Seaview for families and singles, to Point O" Woods for socialites. From Sayville, ferries go to Cherry Grove and Fire Island Pines, famed for their homosexual populations. The Patchogue ferries go to Davis Park and Ocean Ridge -- singles communities which were among the last to switch from kerosene to electricity. Watch Hill for camping receives some service on the Davis Park ferry. Other, smaller communities are reached by private boats, or by ferries to large communities, from which you proceed on foot.

From Memorial Day to Labor Day, the island has lateral ferry service in the late afternoons, evenings and nights between Kismet, the westernmost community, and Ocean Beach, about mid-island. Randy's and Sally's Water Taxis, listed in the local phone book, travel between all island communities. One note of warning. The ride is bumpy -- all right for short trips but very jarring for a fast trip across the Great South Bay to the mainland. You can also hire a seaplane, for a high price, to get from the island to the mainland. The companies are Gold Coast, Pelham Airways, Suburban Seaplanes and Watair Express, all in the 516 (Fire Island-Long Island) area code.

You can't see the island in a day. Furthermore you wouldn't want to. It's an idyllic place, perfect for nestling into for a weekend of freedom from shoes, cars, phones. All phones on the island arrived after World War II, and some communities still have very few. So you should pick the community that sounds like the closest thing to your idea of paradise and try it for a day or a weekend. Each community has a distinctive character.

Robert Moses National Park was established for daytrippers, with a refreshment stand, parking lot, bath houses and, of course, the magnificent white beach. Moving eastward, you reach the singles community of Kismet, followed by Saltaire, then Fair Harbor, all with their own marinas. Kismet has two restaurants with disco dancing and busy tennis courts. Volleyball reigns on the beach. Weekend evenings at six, you see swarms of people suddenly descend upon one house for a "sixish," an informal mass cocktail party. All singles communities celebrate sunsets with a de rigueur sixish.

Houses, especially those rented by groups of singles, often have nutty names, e.g. Mental Ward and Bottom's Up. They have stiff rental prices; $1,000 for a summer share for one person for every weekend is usual. Saltaire's stately trees shade many churches, with a Catholic core of residents since the turn of the century. Houses here can sell for $200,000 and more -- one of the higher-priced island communities. Point O" Woods and the Pines are two others, with the Pines reportedly the most expensive. Land in Saltaire, and on the island generally, that sold for $100 a lot in the 1940s and $250 a lot in the 1950s now sells for $65,000 or more per parcel. That's three lots, the smallest amount of land that Saltaire zoning laws now permit for construction of one house.

Ocean Bay Park has a large, venerable hotel -- Flynn's, a gathering place on weekend nights in the mid-island section with two other major communities, Seaview and Ocean Beach.

Some hardy folks like to hike for miles along the beach. Walking east from Ocean Bay Park, you will pass exclusive Point O" Woods, whose facilities are not open to the public. All the houses here, many of them huge, are of the same gray shingle material, to form a quaint, old-fashioned, even dreary enclave.

Next door sprawls Sunken Forest with centuries-old trees, dwarf pines, grapes, exotic and brilliant-colored flowers, holly, intriguing undergrowth -- and lots of the ubiquitous, shiny red poison ivy found all over the island. In summer, naturalists conduct guided tours through this sunless preserve with an oddly prehistoric ambiance. For basic information about all of Fire Island, including the forest, call 1-516 -- 289-4810.

Beyond the forest is Sailors Haven developed for boaters, with a snack bar, pump out station, souvenir shop and pay phones. By now, you're firmly on the eastern end of the island, where you find Cherry Grove and its next-door community. The Pines -- both predominantly homosexual.

A well-known feature of Cherry Grove, with its imaginatively decorated houses, is the Ice Palace, a swinging, all-night dance hall, home of costume balls and beauty contests. This year, the ghosts of AIDS victims have cast a pall over the traditional unabased hedonism. But Cherry Grove is surviving with its usual patina of joie de vivre. The Pines has savoir-faire, with many famous summer renters and homeowners, not all gay, many in the arts and fashion, with a few score swimming pools. The marina has exquisite, sleek boats that look like the essence of sex and money. The Pines is also famous for its sidewalk, called the Rollercoaster -- a concoction of wooden slats that dip and rise. If you're in the know about the residents, you can tell who is in what frame of mind by counting the number of times someone falls off the Rollercoaster at night.

Some communities have guest houses and hotels. In Kismet the Bulkhead overlooks the bay, Camelot is near tennis courts, with prices approaching $200 for a weekend. The Bayberry Inn, Clegg's and Hotel Hauser as well as various bed-and-breakfast style accommodations, are in Ocean Beach.

Ocean Bay Park has the Seashore Motel on the bay, mostly for seasonal rentals, in addition to Flynn's. Cherry Grove has the Beach Hotel and Club and the Cherry Grove Inn, a little place with nice rooms, some with decks, and a few guest houses. Guest houses are comparatively budget-priced.

Fire Island Pines' Botel charges high prices for weekends. A most scenic area, but try to sleep at night in the hotel, while the music lingers on until 5 a.m. Further down the island, Davis Park has the Leja Beach Casino on the dunes, with a fine sound and sight of the ocean on this verdant part of the island. Camping is free of charge at Watch Hill, but you must reserve in advance by calling 1-516-597-6633, Monday through Friday.

Kismet, Fair Harbor, Ocean Beach, the gay communities and Davis Park sport the best and biggest selection of restaurants. Fair Harbor's Le Dock, with the clean ambiance of an ice cream parlor, has nouvelle cuisine as well as simple fare. Ocean Beach runs the gamut from snack bars to Italian restaurants to the popular McGuire's on the bay, where you must reserve a table.

In flashy, sometimes outre Cherry Grove, the leading restaurant is The Monster, with romantic niches, fresh flowers and fine, expensive Continental food. Manhattan newspapers say it has the best food on the island. You must reserve for an evening. If you arrive by private boat for dinner, the marine lets you park.

The Pines has a few elegant restaurants, the oldest of which is the Blue Whale in the Botel area. A restaurant by day, the Blue Whale turns into a disco-tea dance deck in the late afternoon, then an elegant restaurant again at night. Sip Mersault there under a starlit sky on a soft, summer evening, as the lights glisten at your feet in the marine, in one of the prettiest settings on the entire Atlantic coast. Where Cherry Grove may suggest frantic sleaziness at times, the Pines is all bronzed and laid-back decadence.

These are the sights and amenities but not the raison d'etre of Fire Island. Amble along its narrow walks from the bay to the beach, wearing sunglasses against the brilliant glare of the sun, and you'll begin to relax immediately. Total unwinding takes a bit longer. But this it the place to do it. All you need for a day or a week is a bathing suit, jeans, T-Shirts and sandals, and a sweater and a slicker for the occasional chilly night or downpour.