Leon Uris is a tough, squat, mod-haired, blunt-nosed son of an immigrant paperhanger. He looks like an old street fighter and ex-Marine, and he is. Though he swears he's mellow now, even "laid back," his hawklike eyes give it all the lie. When you ask a dumb question ("What are the Irish really like?"), he tells you so to your teeth. He talks fast. He's sure of himself. Patience is not a virtue.

"Oh, no, Lee's not hard to get along with," says Jill Uris. "So long as I do what he says."

Leon Uris is 53, though he has a habit of uppiing it to 54. "Well, I'm in my 54th year," he laughs, when his wife calls him on it. He is the author of eight novels, five of them No. 1 bestsellers. At last count, "Exodus," his all-time blockbuster, has been published in 50 languages. He has written film scripts, a (failed) Broadway play, a couple of coffee-table picture books.

He has also written a 15-page, single-spaced, third-person biographical resume. It is a curious document, this resume. A bald digest of a controversial life. The major happenings are all here: the operetta he wrote at 7 when his dog died. His failed first marriage. "The marriage of two decades was now running a rocky course." The suicide of his second wife, an Aspen silversmith, who was found one morning in fresh snow, following a quarrel, dead from a 38-caliber pistol. The two had been wed six months.

"Most of what caused her action will remain a secret, forever," states the resume.

Here he is (page 7) getting canned by Otto Preminger during the making of "Exodus." Now Harper & Row is (allegedly) reneging on a contract. Hitchcock bounces him from the screenwriting of "Topaz." See him the victor in a seamy London libel trial; mailing back a key to the City of Baltimore; researching "Trinity" in earshot of Belfast sirens. Here he is, too, marrying Jill Peabody, 22 years his junior, at the Algonquin Hotel. It takes a measure of guts - not to say ego - to construct a vita like that, laying it all out.

On this day the writer who never finished high school is back on his home turf. He is in Baltimore at the invitation of Johns Hopkins University - giving a public lecture, handshaking if not hobnobbing with academic literati (John Barth, for one), meeting the storytellers of tomorrow in seminar.

He also manages while he is in town to get by the old homestead at 1908 Minroe, a rowhouse with marble steps. It still stands. So do Paul Edlowitz, the butcher's kid, and Yummie Schless, with whom he used to hike it across the 29th Street bridge on his way to City College (a high school, where he flunked English three periods running). His parents split up long ago, Uris says, and his dad, 80, lives in Philly now ("My books have been his food and drink and alter ego for many many years"). But he finds a few old relatives. In short, the trip back is a homecomming, if not weepyeyed, warming all the same.

Uris and his wife are in the university guesthouse. Uris is clad casually: flared slacks, burnt brown loafers, a tan shirt with epaulets and French cuffs. He leaves the shirt unbuttoned, revealing a thatch of snowy hair and a large gold ornament dangling from his neck. The ornament, an Irish cross, was given him by his wife, he say. "I wear it as a wedding ring."

The topic has just shifted to successful writers. There are fewer extant in America than well-diggers, astronauts, or hummingbird watchers. The reason, not counting talent, which damn few have, is a dread of going to that "small, dark, lonely room." Robert Penn Warren once described it as "daily going naked into the pit." It takes intestinal fortitude.Uris has had it for a quarter of a century.

"I think I've dredged up some important problems, along with all the commercial success," he is saying. "I'm no Solzhenitsyn. I don't have his kind of message. I know they never mention me with the American sweethearts. But I'll rest on my titles. I've written two novels - 'Exodus' and 'Trinity' - that have had a world impact. Things could be worse."

A tiny pause; his hairless right hand is pyramided on his forehead - a kind of struck nonchalance. "I'm not going to evaluate myself beyone that - cause if you ask me I think I'm the greatest goddamned writer alive. You figure out my place."

Mrs. Uris, a tall, deep-voiced, youthfully attractive woman in black slacks and a pair of flats, interjects. She has been packing bags in another room and has come in to hear this last.

"One of the things I think we've talked about, Lee, is that you're a unique number - the modern historical novelist. One thinks of James Michener, too, but he's not the same thing, really. He's more a chronicler of epics, I think. You put mrre feeling, or at least personal intensity and subjectivity, in your writing."

"Make sure you quote HER as saying that," says Uris. Pouring on Facts

Later, he professes an admiration for Michener's prolific research - probably greater than his own. "It's fascinating how he picks up a piece of territory." He was once on the Mike Douglas show in Philly, Uris says, along with Michener and Pearl Buck. The three got introduced off-camera and ended up talking the whole while about Frisbee. "Some heavyweigths."

Picking up a piece of territory - pouring the lava of fact, at one critic put it, onto a runaway story, is the particular genius of Leon Uris. This is not Harold Robbins or Jackie Susann or Sidney Sheldon writing. This is someone whose passion is the sweeping historical event. That and getting it going from the opening sentences. As in "Trinity": "I recall with utter clarity the first great shock of my life. A scream came from the cottage next door." Or as in "Exodus": "The airplane plip-plopped down the runway to a halt before the big sign: Welcome to Cyprus."

For a man who has spent words like a drunken sailor, Uris never has seemed to waste them.

The critics haven't loved him, he knows. One wit once suggested you could work out actuarial tables or maybe solve Kant while reading a Uris novel. Someone else said Uris' books aren't serious literature, but journalism "prefabricated for Hollywood movies." "None of it's been enough to make me change one comma," says Uris. "I have no faith in criticism as a teacher."

Though later, circling back, he says: "I'm human. If I get a bad review at breakfast, it bothers me. If it's a good one I read it five or six times before it goes into the scrapbook." Beloved Ireland

Ireland moved him, Uris says. He and his photographer-wife went over in 1972, ended up staying most of a year, traveling 10,000 miles, fanning out from a flat in Dublin. Now he tells audiences of "my beloved Ireland." As if St. Brendan baptized him.

The country meant a new culture, new history, new religion, new people. But the result was two books: his sprawling - and for once favorably reviewed - novel (which has sold 1,600,000 copies in hardback alone) and her well-received photo study (with his accompanying text), "Ireland: A Terrible Beauty.? It was the high point of a career.

"'Trinity' was an important book to write," Uris says. "It destroyed an essential myth: that I'm a Jewish writer." For all the apparent ironies of a Jew in Ireland (some snickered he was trying to write an Irish 'Exodus'), he thinks there must have been something percolating in his head for years to get him to go there. In point of fact, he similarities between the two peoples are startling - from their twin cultural impact on America to their unique languages, literary traditions, and reverence-fear of rabbis and priests.

"Christ, I can even compare the potato famine to the Holocaust. I call it the 'gentleman's genocide.'"

The Irish are lovely people, says the man whose name is a Hebrew derivative for "Jerusalemite." "But the writers have a way of leaning on their shovels." In the pubs.

Writing would make anyone want to lean on his shovel. "You are subjecting yourself to tough things as a writer. It erodes a person. That's why the casualty rate is so hight. You fear the exhaustion of your reserve, the collapse of your ambition, involuntary retirement by your readers. The psychic drain is enormous." Parting Wisdom

There was a time, after the suicide, when he was sure he'd never write again. "You're married to a girl six months, get into an argument, she kills herself. It's about as low as you can go." He seems about to say more, doesn't. He excuses himself, saying he wants to collect a few things in the other room.

Jill talks. "We met just three months after Margery's death. My feeling was that here's this man who badly needs help. Quite frankly, he was in extremely poor condition. It was a time in my life when I personally needed to give to someone. After we fell in love, nothing mattered."

Her parents, proper Bostonians, didn't see it that way. "I was getting it from them all the time. They'd say, 'This is a man who's recently divorced, whose new wife shoots herself, who is 22 years older than you. My God, girl, what are you thinking of.'"

But things worked out. In 1970, Jill has a freakish accident in a beach vehicle on Lon Island. It required brain surgery. This time her husband nursed her back. They've been married eight years now, do everything together. In fact, they're off from their mountain retreat in Aspen once again - Israel this time, where she'll shoot for another photo book, and he'll research for another blockbuster. "Just say it'll probably take up where 'Exdous' left off."

He beams. "You know, I made more for each page for 'Exodus' than for all of 'Battle Cry,' my first novel. I'm not totally secure, which I know shocks you, but it's the truth. I've lived very, very well. There are few multimillionaires in this business. It's just not in the cards. But at least now I have the luxury of time."

Any parting wisdom "If anyone out there wants to be a writer, I'll put him in business. I'll give him his first sheet of paper. And oh, yes: If you don't give yourself 20 years to make it, you're kidding."

At the end of that odd 15-page resume, there is this: "In short, one must apply the seat of one's pants to the seat of the chair and write. There is no other way." He grins. "So write."