His dark materials: Don Winslow makes the transition from cult author to household name

He's the crime writer who captures the seedy underbelly of California – and Hollywood's current go-to author. Guy Adams spends the day with Don Winslow.

I meet the novelist Don Winslow at his local coffee shop in Solana Beach, a bright, breezy surf town just north of San Diego, California. He comes here each morning, after a session at the typewriter, to re-caffeinate, watch the world go by, and top-up a well of inspiration that has informed 16 remarkably successful books over the past two decades. Winslow sticks our drinks on a tab, exchanges small-talk with the staff, and grabs a seat under a sun umbrella. Then he tells me about 'The Godfather'.

For as long as Winslow can remember, an elderly man with an expensive wristwatch has also spent mornings at a nearby table. There is something odd about this guy; a touch of what you might call the Don Corleones. "I see the way people talk to him, the way they act round him, and I think, 'He's got to be some sort of Boss'," Winslow says. "A while back, and I swear this is true, some kid just walked up and passed him an envelope full of banknotes. The kid didn't say a word: just handed over this pile of cash, and then walked away."

One day, Winslow asked the strange man his name. He wouldn't say. Still won't. So now Winslow just calls him The Godfather. "We see each other most days and make small talk. He laughs. I laugh. We have a good time." At some point, The Godfather will probably crop up as a character in one of Winslow's novels. "That's the thing about being a writer who lives and breathes a place like this," he says. "My problem is not that there are too few ideas out there. It's that there are too many."

The shady folk that Don Winslow meets every day are central to the fiction which has lately made him one of the hottest novelists in Hollywood. A former private detective, he came to Southern California in the 1990s, and began writing sharp and extraordinarily savvy yarns about the surfers, drug-dealers, cops, gangsters, prostitutes and millionaires who inhabit the region's grimy underbelly. Since then, he's churned out 10 straight bestsellers. And the recent release of Savages, Oliver Stone's movie adaptation of his book, is now turning him from cult author into something approaching a household name.

In Solana Beach, where Winslow, who is 59, lives with his wife, Jean, reality is often intertwined with fiction. A few years ago, for example, he was researching a book on drug smuggling. One day, someone emailed him a video shot by one of the Mexican cartels which controls the flow of cocaine and marijuana into the region. When he clicked 'play', Winslow watched a camera pan slowly past several decapitated human heads, which had been neatly arranged into a row.

The gruesome image stayed with him, and would eventually appear in the opening pages of Savages, a gripping heist story about Ben and Chon, two pot dealers who upset a spectacularly ruthless gang from south of the border. The severed heads also crop up at the start of Stone's film. "A lot of people say the scene is over the top," says Winslow. "Well guess what? I agree. But it's also what actually happened."

The movie version hit the UK last month. f It stars Taylor Kitsch and Aaron Taylor-Johnson as the two protagonists, and Blake Lively as 'O', their mutual love interest. An all-star collection, including Benicio Del Toro, Salma Hayek, and John Travolta take supporting roles. It has so far made $70m (£43.4m) worldwide, against a budget of just over half that, and been hailed by some reviewers as the best thing Stone has done in years. Roger Ebert, doyen of US film critics, called it "a return to form for Stone's dark side" with a "spellbinding" denouement. Variety hailed: "An acidly funny chronicle of sex, drugs, murder and corruption of every stripe".

The Hollywood success is rubbing off on Winslow. Movie rights to nine of his 10 most recent novels have been snapped up. They include a ripping surf yarn, The Winter of Frankie Machine, a detective book, California Fire and Life, and a thriller, Satori, slated to star Leonardo di Caprio and which Warner Brothers aims – according to the trade press – to leverage into "its own Jason Bourne-type action franchise".

Winslow, who is small and has what he calls "a face people forget", finishes his coffee and asks if I fancy a walk through the town he calls home. We cross train tracks that connect Los Angeles with San Diego, and turn along the Pacific Coast Highway, which has been ferrying beautiful people from beach to beach for as long as the Californian Dream has existed. We pass grimy tramps, be-suited salesmen, tattooed surfers in knackered vans, and girls in bikinis driving open-top cars with absolutely no sense of irony.

The scene could have been pulled straight from the realm of Winslow's fiction: a world of superficial wealth, and endless sunshine, which he lays down in cinematic prose that echoes Frederick Forsyth and James Ellroy. Up the coast, he points out Swamis, a world-famous reef break that features in his renowned surf novel The Dawn Patrol (in the book, he called it 'Gurus') On the beach, the vibe, to quote his newest book The Kings of Cool – is "classic BB" (Basically Baywatch). We reach a dive bar, where they sell cold beer with hot pizza. It's time for lunch.

Don Winslow's gifts, as an author, can be neatly divided into two realms. Firstly, he knows how to churn out the sausage that is a bestselling novel. Reviewers call his plots "gripping" and his books "hard to put down", and if they are as generous as Janet Maslin, of the New York Times, they proclaim them "too damn good to be polarising". But the fizzle is only the half of it. Like any really great writer, Winslow's prose carries a deeper wisdom: an ability to bring a place and its heritage alive.

Take The Dawn Patrol. On the surface, it's part detective story, part surf caper. Underneath, it's actually about how the post-war Californian Dream ended in smog, traffic jams, and the abuse of illegal immigrants. Savages, meanwhile, is both a gripping heist story, and a remarkably astute history of organised crime in Orange County, from the 1960s to the present. And you'll learn more about the Mexican drug trade in his 2005 novel The Power of the Dog, than in years' worth of newspaper coverage.

Winslow collects ideas, big and small, the old-fashioned way: he talks to people, from the guy next to him in a surf line-up to the man who runs his local taco truck. "People say there's no history out here. Sure there is. Just ask people. You can't drive anywhere without seeing it. Take La Costa, the old resort up here east of Carlsbad: built with teamster union money. The bridge to Coronado Island off San Diego was built because the mob had a hotel there and needed a way to get people out there."

He gestures in the direction of the sea. "Floating bales of marijuana have been dropped off right here, and fishing boats brought them back," he says. Half an hour away is Dana Harbour, which crops up in the drugs yarn The Kings of Cool. "There are hundreds of boats in that place, and hardly any of them ever go out. So what's in these boats? And where did the money come from? Some of them must be going out to sea and getting drugs. I get very excited about this kind of shit."

Winslow always wanted to be a writer. Born in 1953, the son of a Navy veteran who'd seen action in the Pacific, he grew up in the Rhode Island fishing town of Matunuck. His mother was a librarian, who'd encouraged her kids to read widely, and he came of age on Shakespeare, Fitzgerald and Hemingway. "In the evenings," he recalls, "I would sit around, and my Dad would have his Navy buddies over. They'd drink a few beers and tell stories." It remains a literary family: his sister, Kristine Rolofson, has published no less than 35 romance novels.

After leaving university in the mid-1970s, Winslow moved to New York, with a vague plan to make a living from writing. Instead, he fell into private detective work. The unplanned career began when a friend, who had become manager of a cinema in Times Square, hired him to pose as a junior employee and work out which staff members had their hand in the till. He soon uncovered a major scam: "Staff would go round at the end of the night and pick up the empty popcorn containers. And ones that didn't look too bad they'd put back on the counter, because the accounting was done by container." He still never eats in a cinema.

Before long, Winslow was also put in charge of catching pickpockets who were targeting customers. Then he joined a professional detective agency. "It was exciting. At times a little too exciting. You got into fights. And I'm small." Writing stayed on the back burner until the late 1980s, when he heard a radio interview with the detective novelist Joseph Wambaugh. "He said that when he started out, he decided he was going to write 10 pages a day, no matter what. I was a big admirer of his. I used to read him on stake-outs, along with Elmore Leonard and James Ellroy. So I thought I should write five pages a day. And that's what I did. Eventually I had a book."

Winslow's first novel, A Cool Breeze on the Underground, came out in 1991. It did well enough to persuade publishers to buy a sequel, but not so well that Winslow could give up the day job. By the mid-1990s, he had churned out four other detective books which had all experienced a similarly mixed fate. On the detective front, after a spot of industrial espionage, and some undercover work investigating drug use among employees of a major corporation, he moved his wife and young son (who is these days a staffer for the Obama re-election campaign) to California.

The housing boom and subsequent crash had led to a spate of suspicious house fires across the region. Winslow was paid by insurance companies to establish which ones were accidents, and which involved arson. But what he really wanted was a career change. "I knew I should get out of the PI business the day I was looking through pictures of a woman whose husband had burnt her to death. I found myself flipping through photos with one hand and eating a ham sandwich with the other. I needed out. I'd got too hardened."

In 1997, Winslow got that wish. The previous year, he'd been commuting five days a week f via train to Los Angeles, where an arson case was in court. He began writing a new novel en route. The relatively short journey time forced him to adapt to a more staccato prose style than before; faster, sharper, and breezier. "When I'd hear the conductor say, 'Union Station 10 minutes', I'd wrap up a chapter. And I'd do the same thing on the way home. It was so different from anything I'd ever written before. I also started writing in the present tense. And it worked."

Within a few months, he'd finished a novel: a hostage drama called The Death and Life of Bobby Z. It was different from anything he'd written before. And better. His agent decided to see if he could sell the film rights. Within days, a full-blown bidding war had broken out. By 5pm on the Friday after he'd finished the book, Winslow found out that he suddenly had "more money than I'd ever had in my life". He promptly bought a horse ranch, in the Californian mountain town of Justin, where he now spends part of the year. "All of a sudden I could be a full-time writer."

Since then, Winslow's life has followed a fairly simple routine. He wakes up at 5am, writes for a few hours, and then goes for a long walk. In the afternoon, he'll revise his morning's work and then head out for a swim, or a surf. At any one point, he keeps two novels on the boil, switching projects whenever one gets bogged down. He calls writing "a kind of addiction", and never goes more than a few days without it.

Not everything's ended happily. The film version of Bobby Z went straight to DVD. Other movie projects languished for years in development. But the hit novels keep coming. There have been nine focused on a patch of Southern California he says stretches from Newport beach to Tijuana, "where I know the bars, the restaurants, the surf breaks, and the people". He hopes they will eventually tell the "complete history of crime in this region, over the past 40 years".

We've finished our lunch now, and Winslow heads down to the beach, to shoot pictures and check out the waves while we still have daylight. Tall cliffs stretch into the distance, fringed by wide, white-sand beaches. Surfers bob around a couple of hundred yards off shore. Bronzed men look out from lifeguard towers. It's a picture-postcard scene. But Don Winslow wouldn't be Don Winslow if he didn't see a bit of darkness.

"In Southern California, you see this richness everywhere: the good life, the beautiful people; all that stuff," he says. "But then you also know that, if you look deeper, something ugly is going on behind the scenes. As a surfer, I think of places like a wave: you see one thing on the surface. But you always know there's something different going on underneath."