‘LET ME ASK you a question,” George Pelecanos says as our interview comes to an end. “Are you a Thin Lizzy fan?” Given my Dublin connection, he has been itching to ask it all along. “I just think it’s an amazing story,” he says. “I get chills when I think that there’s a statue of Phil Lynott on a street in Dublin, that people leave flowers by the statue. I love stuff like that.”

Music has always played an important part in George Pelecanos’s novels. From his debut A Firing Offense in 1992, his characters have prowled the mean streets of Washington DC, tapping a toe to a bewildering variety of sounds, from the swing jazz of the 1930s through the funk rock of the 1970s and on to the contemporary sounds of last year’s The Cut. In fact, it was music that taught him how to write his own way.

Pelecanos wasn’t much of a reader until his mid-20s – “Until then I wanted to be a filmmaker, I was a real film nut” – but then he took a class in classic crime fiction. The curriculum included Dashiell Hammett, Raymond Chandler, Mickey Spillane, Ross Macdonald and James Crumley.

“All these books blew me away,” he says. “I mean, even an early Mickey Spillane, that’s a good book. I got obsessed with books after taking that class. And by books I mean crime novels.”

Rejecting the notion of a formal writing class, Pelecanos instead chose to immerse himself in reading. “It took me 10 years before I sat down to write my first novel,” he says. “By then it was the 1980s, the punk thing had happened, and I was heavily involved in that. And I got the idea that what I was going to do was write a punk rock detective novel. I was writing a book without any training, just like those guys were picking up guitars without any music lessons. And I was proud of that, because I had never taken a writing class. I didn’t know how to write a book. But I thought I had something to offer. So I just did it. And to my surprise, it was bought by the first publisher in New York who took a look at it.”

His current novel, What It Was, is his 18th. It reprises one of his series heroes, and Pelecanos’s favourite among his own creations, Derek Strange. An “origins” tale, it’s set against the backdrop of Watergate in 1972.

“It’s a lot of fun for me to write a book set in that time,” says Pelecanos, “because I actually don’t do a lot of research for those 1970s books. It’s still very close in my memory. I just let it go, I let it roll.

“I was 15 years old in 1972, and yeah, when the 1970s broke I was out there. Everything was kinda swirling around me – the music, women, cars, the culture. And it was really the best part of all that, because all those people in the 1960s had done all the work for you, they’d kicked the door in. So now you were there just enjoying it.

“Smoking weed, free love, and all that went with it . . . It was before coke really came to town, before Aids, all these things had yet to enter the stage. I mean, it was the best time to be a teenager, believe me.”

What It Was also offers one of Pelecanos’s most persistent themes, that of fathers, present and absent. Early in the novel, asked by a potential client as to why he operates out of an office, Derek Strange tells her that he’s showing the young black men on the street that a black man can “build his own thing”.

“Derek is a pretty flawed individual,” says Pelecanos, “but he wants to get that part right. I mean, when you read the books where he’s an older man, you know he has fidelity issues, he can’t be faithful to one woman. At the same time, he wants to stand up for these kids. But you know, he’s just like most men. There’s some good things you do and there’s also some things where you fall down.”

Meanwhile, the novel’s antagonist, a wannabe gangster called Red “Fury” Jones (based on a real-life killer of the time called Cadillac Smith), is described as being a fatherless son.

“You only have to look at the statistics,” says Pelecanos. “Kids need a father around to make them whole, they need their mom. Guys who feel like it makes you a man to make babies, they’re completely misguided. It makes you a man to be a father. And I’m not moralising about marriage or anything. I understand that people split up, and marriages don’t work out, and people do the best they can. But if you’re going to not be there from the very beginning, then don’t do it.”

Concern for the marginalised also infused Pelecanos’s work on groundbreaking TV show The Wire, which was set in Baltimore and on which he worked as a writer and producer alongside David Simon, Eric Overmyer and Ed Burns.

“You always hear, in the States at least, people say: ‘Why can’t that kid get a job? Why does he have to sell drugs? Why doesn’t he just go to university and get out of the ghetto?’ And what we did with The Wire was, we showed you why. We showed you how all these pieces fit together to conspire against these kids who are born into this particular place, through no fault of their own; it’s a complete accident of birth, and they just get left behind. From day one, they’re just way behind everybody else.”

He’s keen to stress the extent to which The Wire was a collaborative effort. “A lot of novelists,” he says, “they’re not exactly anti-social but they are solitary people who don’t do well if left to prosper on their social skills.” He chuckles. “But I just liked it from the beginning. I was fascinated by the process and how all these talented people come together and make this thing happen. It can be art, if you’re doing the right thing.

“I didn’t really get it, until probably the third season, that we were really on to something. That was when we started bringing in people like [writers] Dennis Lehane and Richard Price. And then it was like, ‘Yeah man, something’s going on here. We’re catching lightning in a bottle.’”

These days Pelecanos spends six or seven months per year in New Orleans, where he’s co-producing Treme with Simon and Overmyer. The similarities between Washington DC and post-Katrina New Orleans are obvious.

“Well, they’re both Southern cities, and they’re both black cities, if I can say that. Y’know, DC’s majority black, and New Orleans is majority black. So when I came down here I was very comfortable, because if you close your eyes and listen to the voices, it’s very much like Washington. Actually, it’s friendlier. And, in some ways, deadlier.

“The crime rate down here is the way it was in DC ten years ago – it’s very dangerous. But it’s also alive.”

With his flair for writing about music, cars and clothes, George Pelecanos is arguably the coolest crime writer in the US right now. What makes him a great novelist, however, is his abiding compassion for those who, as Jim Thompson put in it The Killer Inside Me, “started the game with a crooked cue”.

“I think what sets you apart or makes you better is that eventually you get honest,” he says. “It’s funny, because some of the bigger books with social themes, you think those are the ones that will get remembered. But I’ve found that when I went around on these book tours over the years that people were always mentioning books like Shoedog and King Suckerman, which were really straight-ahead books. They don’t make any pretence of being socially important, or anything like that. And I’m cool with that. I don’t care if people call me literary, they can call me anything they want. What It Was is a pulp novel, but I think it’s a hot one.

“I think the books will stand on their own. That’s always been my goal, to write books that’ll stick around for as long as they can. And the way to get them to do that is to give them some weight.

“But that’s what everyone’s aiming for, a kind of immortality. We’re trying, even though it’s a futile goal.”

What It Was by George Pelecanos is published by Orion Books