Some afternoons he sits in his cabana staring out at the sea, staring and staring, and people come by and say, What are you doing? Why aren't you working? And he tells them he is writing a novel, and they can't understand it.

Lawrence Sanders spends four hours a day putting words down on legal pads in longhand. How many hours a day he spends thinking, he has no idea.

His two successful novels about Africa won lavish praise for his insider's knowledge of that scene, though the only time he was ever actually on the continent was when his ship put in at Algiers for two days during the war. His phenomenally bestselling detective thrillers are based on casual conversations with a couple of cops he knows, and a huge amount of reading.

And thinking.

What he writes is real enough for his readers (except maybe the time he forgot that revolvers don't have safeties). So far, they have bought 25 million paperback copies and 1.5 million hardcover copies of his 20 books. Last week his latest, "The Fourth Deadly Sin," was No. 2 on the New York Times hardcover list while "The Passion of Mollie T." was No. 2 on the paperback list. He is published in 15 languages.

"I knew a detective in New York," he says, "but I never interviewed one in my life. I read the newspapers, nonfiction, detective stuff."

At the moment he is fascinated with the Civil War, histories and memoirs. He is rereading "A Tale of Two Cities" to study the way Dickens wove politics into his story.

"I don't want to be prejudiced by reality," he laughs, "but it's got to sound right. This apartment house has 300 apartments, it's like a small town, and I hear things you wouldn't believe. Can't use 'em, of course, I'd get sued. If I put it in a book, people would say, Boy are you kinky. But there's so much stuff all around. I just read in the papers about this guy who holds up three banks with an underwater spear gun. He apparently thinks it's not technically a weapon. Things like that are almost impossible to imagine."

Sanders' most famous hero is a retired New York chief of detectives named Edward X. Delaney, who started as a relatively modest character and was promoted by popular demand. Delaney is a big, stolid man with a gray brushcut, shoes laced up to his ankles and a heavy tread. He eats sloppy Dagwood sandwiches standing over the sink but is adored by his handsome wife. His methods involve classic police procedure, an unexpectedly quick intelligence and long, weary experience of the human race.

This is what Sanders is thinking about, out there in his cabana: the inside of Edward X. Delaney's mind.

"I don't like him," Sanders confesses. "I think he's an old expletive . An opinionated, pontifical SOB. But the readers love him, mostly the women. I don't understand it. The guy took on a life of his own. I put him in 'The Second Deadly Sin' and 'The Third Deadly Sin' and dropped him, but people kept asking when there'd be another Delaney."

By the time Sanders set about "The Fourth Deadly Sin," about the murder of a psychiatrist, his first "sin" book since 1981, he had forgotten what Delaney looked like, so he had to hire a researcher to read the earlier books and remind him of the man's habits and dimensions and the color of his eyes.

A Sanders hallmark -- along with his preoccupation with violent death and the obligatory sex scenes -- is his tireless descriptions of food and drink. Every time a character stops off for even the most casual snack, each dish, drink and condiment, and the way it is eaten, is dispassionately examined. In one book he devotes four pages to a woman cleaning her apartment, complete with the brand names of the scouring powders and the 3-in-1 oil with which she lubricates the door hinges.

"It's a way to describe characters," he says. "You don't get someone across with a lot of heavy psychological stuff. It's what they eat and drink, what they wear, that tells you about 'em. I happen to be a sandwich freak myself. I love the bagels here, the pita bread, all those things. One woman wrote me that the minute she read about Delaney having a pastrami on rye with sliced Bermuda onion and mayo, she had to put down the book and go make herself one. I told my publisher, I'm gonna have the fattest readers on the market."

One suspects that Sanders has bequeathed rather more than his sandwiches-over-the-sink habit to his creation, dislike him or not. The digressive debates on psychiatry, the Equal Rights Amendment and politicians vibrate with strong feeling. "He rarely complained about the weather," the author writes of Delaney. "He was constantly amazed at people who never seemed to learn that in the summer it was hot and in the winter it was cold."

Surely that's the author talking. But he never quite lectures. He's been around too long for that.

Been around is right. For more than 25 years Lawrence Sanders wrote gags at $30 a week for short-lived cheesecake magazines ("oh how we worried about cleavage; nowadays they'd look like the National Geographic"), slogged through the gray world of magazines like Mechanix Illustrated and Science and Mechanics, writing, editing, composing captions ("I was thinking in cutlines; my thoughts were coming 14 picas wide") and writing pulp stories on the side for $75 a whack.

"At that rate of pay I learned to write fast, knock it out, no outline or anything. I was a great reader of detective and spy fiction. And then finally came the time when I read one and said, Hey, I can do better'n that."

It was 1968. His magazine was running a lot of articles on bugging devices -- the cocktail-olive transmitter with the toothpick antenna -- and he had started a novel about an apartment house robbery caper.

"The first scene was two guys talking on a park bench in Central Park. I read it over and it was like a hundred others. Then I thought: What if someone had a tape recorder under the bench for some reason and wrote a report?"

So he did the entire book in the flat language of documents: surveillance reports, wiretap memos, police records. He called it "The Anderson Tapes."

"I'd met this agent at a party, told him about my novel, and he said, Oh yeah, well if you ever finish it, send it along. So I did, and he read it and said, Oh yeah, I can sell this. Sent it to Putnam's special detective fiction division. Then he called me back, it happened so fast, and said, They love it, we got a sale, only it's too good for the detective division, they want it in the general trade division."

Sanders got a $3,000 advance. A week later the agent called to say he'd sold the paperback rights to Berkley for $210,000, and a week after that the movie rights went for $100,000.

He quit his job and set to work writing fiction, which was all he had ever wanted to do since he got his first byline at age 12 in the school newspaper. For three years nothing much happened. Love stories, "The Pleasures of Helen" and "Love Songs," came out of his trunk and were published quietly. Then, in 1974, he wrote "The First Deadly Sin," about an ice-ax murderer who kills as an intellectual exercise: another blockbuster, another movie sale, and he was on his way for sure.

"Roman Polanski was gonna direct it, and he called me and we talked for half an hour about the personality of the killer. I didn't want to tell him I:

"May we sit down, please?" Delaney asked. "I'm worn out from the climb. My name is Delaney and this is Sergeant Abner Boone."

"Sergeant . . . " Gerber said in his gravelly voice. "I was a sergeant once. Then I got busted."

A neat nugget of character development there, if you don't mind the fact that people don't really speak this way. Even his bit players are incorrigible chatterboxes.

"I'm not talking about writing 'War and Peace,' " Sanders says. "I'm talking about building a chair. It's a craft."

He doesn't need to write another word all his life, of course. He could, as he says, throw his typewriter into the ocean anytime.

"I lead a dull life," he says. "If my financial success had come at age 25 instead of 50, I'd have bought yachts, everything would be different. But my style of living hasn't changed all that much. I don't travel, except to my place in New York twice a year. I drink the same vodka, the same cognac I did before. I don't have any hobbies. I read . . . and I write."

And cooks. He finds cooking as creative as writing and likes to kid his editors about putting out a sandwich cookbook over Edward X. Delaney's name.

Sanders and his wife of 35 years, Fleurette Ballou, who have no children, have lived for the past eight years in a high-rise apartment here, with a separate office for him that overlooks the long, long Florida beach and the stucco slurbs above Fort Lauderdale. And the cabana, where he treats himself to his daily vodka and a pipe. Dozens of pipes are piled like kindling in a huge ashtray on his desk. The bookshelves are filled with copies of all his books in languages from Hungarian to Japanese. On another shelf stand reference books and the two-volume Oxford English Dictionary. The refrigerator is stocked with soft drinks and sandwich makings.

He doesn't even own a car.

"Luck, luck, luck, what can I tell you," he says. "Ezra Pound said, It's gotta be new. New. What's that great opening line from Sabatini? 'He was born with the gift of laughter and the sense that the world was mad.' I feel sorry for the first-novelist today. It was a lot easier then, publishers would actually look at your manuscript. Now it's all run by big conglomerates. Products. Like cornflakes."

Born in Brooklyn 65 years ago, Sanders was raised in Indiana, graduated from Wabash College in 1940. From 1943 to 1946 he was in the Marines, served as a sergeant with a detachment aboard the battleship Iowa. His father was an accountant for an engineering firm, "worked hard all his life, died at 72, and I make more in a year than he made his entire life. Life is unfair. And to get paid for something you enjoy . . . there's guilt there. Another deadly sin."

He reads experimental novels now and then, nibbles at modern poetry, but finds it all too specialized, obtuse, self-indulgent. "Writing is communication," he says. "You want to know someone's out there, otherwise what's the point of it?"

The vision of life that Lawrence Sanders communicates has been called depressing. The sweaty sex, the deadpan descriptions of sadistic killings, the downbeat endings -- Delaney has an unattractive tendency to toy with his villains until they destroy themselves -- leave some readers slightly queasy. Sanders says that's just the way things are.

He looked up suddenly and beyond the city's glow saw the stars whirling their ascending courses. So small, he thought. All the poor, scrabbling people on earth caught up in a life we never made, breaking ourselves trying to manage.

Philosophers said you could laugh or you could weep. Delaney preferred to think there was a middle ground, an amused struggle in which you recognized the odds and knew you'd never beat them. Which was no reason to stop trying.

"At the age of 78 I'll still be at the typewriter," he chuckles, "and I'll be writing, ' . . . and then her firm white thighs . . . ' and fall over the keys. That's the way I want to go."