The bookshop manager finishes his introduction, and Ellroy walks forward, yapping and howling, pausing to cock his leg against the lectern and make some gushing noises. He explains that he doesn't write his own books: he is merely channelling for Barko, the bull terrier with whom he is pictured on his book jackets. Then he begins the audience participation segment of the evening: Barko wants to talk to us, he explains. Barko wants us to know that he has slept with the most desirable women of the century, and if anybody cares to name a year of this century, any year, Barko will tell us the name of the key woman he was with. Sixty-six, somebody calls. Ellroy, quick as a flash: "Julie Christie, right here in swinging London - putting the horns on Warren Beatty." Forty-three? Zip, he's in there: "Ingrid Bergman - Robert Rossellini cornuto." Thirteen? Again, no hesitation: "A very young Gloria Swanson - Joseph P Kennedy cuckolded."
You may have spotted this for yourself, but James Ellroy likes to perform - less demon dog, in fact, than circus dog. Perhaps, as he says, "I am as exuberant as I am and as good a performer as I am because in some ways it's a reaction to how hard I work." The sense of performance comes across strongly in his latest venture, a television film called White Jazz, broadcast this Saturday as part of Channel 4's controversial season of erotica, "Red Light Zone".
In part, the film is an exploration of the landscape of Ellroy's "LA Quartet" - four novels (The Black Dahlia, The Big Nowhere, LA Confidential and White Jazz) in which he recreates the Los Angeles of the Forties and Fifties, showing a town full of corruption and crazy sex. Ellroy takes you around some of the key locations, and tells you about the real-life characters who populate his books, some of them (Howard Hughes, the gangster Mickey Cohen) under their own names, some in disguise. Chief among these is the late Freddie Otash - also known as Freddie O and Shakedown Freddie - a corrupt policeman who acted as fixer for the studios whenever stars were being blackmailed, breaking a leg here and there, and as fact-checker for the scandal sheet Hollywood Confidential; in this capacity, so he told Ellroy, Otash had hotwired every gay bathhouse in LA to see if he could record any famous voices.
The other part of the film concerns the murder of his mother, Geneva Hilliker Ellroy, by an unknown man in June 1958. The Ellroys had divorced four years earlier, and the 10-year-old James was living with his mother in El Monte, a few miles east of Los Angeles. She was an alcoholic and, by her son's own account, "somewhat promiscuous - not outrageously promiscuous by today's standards, but certainly that way by 1958 standards." She was last seen leaving a bar with an unknown man and a blonde woman around 10pm on a Saturday night; her body, strangled with one of her own stockings, was found the next day dumped in some bushes next to a high school playing field.
The murder was never solved. But Ellroy has now re-opened the case - the demon dog turns bloodhound - with the help of Bill Stoner, a former sergeant in the Los Angeles County Sheriff's Office. In America, where there are fewer secrets than here, it's possible to get access to police files; armed with these, Stoner and Ellroy are re-interviewing the surviving witnesses and following up some leads. Their main hope, though, is that somebody - perhaps the blonde woman in the bar - will come forward: "In these alcohol-fuelled rape-killings, the principal witnesses all tend to talk after a passage of time. And there are probably a lot of people out there, some people, who know what happened."
The investigation is to be the subject of a book, entitled My Dark Places - not, you may think, an appropriate title given the degree to which the floodlight of publicity has been shone on this corner of Ellroy's life. It crops up in every interview, to the point where you wonder if he's not exploiting his mother's murder for publicity purposes. When you put this to him, he nods vigorously: "Of course it's publicity, it's all publicity. I'd be the first to admit it... I deliberately set out to use it to sell books." This is not something that troubles his conscience: "If you were my age and your mother had been murdered 36 years ago, you get on with your life. My wife and I crack jokes about it." (The example he gives is not really printable.)
Ellroy can come across as callous, and a touch arrogant - when the talk turns to his books, he starts flinging around words like "epic" as if they were going out of fashion, and he has no qualms about telling you how well-plotted and richly characterised his work is. He's less interested in comparisons with Chandler and Hammett than Balzac and Dostoevsky; indeed he despises most crime writers, Chandler in particular ("I think he's very successfully imitated because there's a lot of cheap-shot writing in there"). Some critics have taken a more sceptical line about his own work, dismayed particularly by his liberal use of racial and homophobic invective - the "kikes" and "niggers" and "faggots" that spatter his dialogue; one American critic wrote that every one of his books is like "a mini Mein Kampf".
Ellroy had a notoriously wild youth, breaking into girls' houses and sniffing their underwear, getting heavily into drugs and alcohol. Now, though, at 46, he's settled down into a milder middle age. Beneath the demon dog exterior, the side of him that gets a kick out of Freddie Otash and fantasies of canine sexual extravagance, there's clearly a moralistic streak, perhaps left over from his Calvinist upbringing ("My mother grew up in the Dutch Reformed Church and sent me on Sundays, and stayed at home"). He's clearly upset when he's accused of condoning the illiberal attitudes depicted in his books - they were simply endemic to the times. He defends the extreme violence he shows on the grounds that he is trying hard to make it seem ugly and shocking. And for all the arrogance about his writing (in my book, largely justified), he is a disarmingly polite and charming interviewee, breaking off from his mineral water every now and then to eulogise his wife ("Easily the most brilliant person I have ever met"). Hardly a demon dog at all, in fact - just a cute little puppy wearing plastic horns.