Imperial Bedrooms, By Bret Easton Ellis

The most revelatory moment in Bret Easton Ellis's debut novel, Less Than Zero, published 25 years ago, comes pages before the end. It offers the reader a rare glimpse into the narrator's otherwise hermetically sealed inner life. Clay, a jaded 20-something living on the fringes of Hollywood, alongside like-minded children of privilege already bloated on LA's excesses, is confronted by his girlfriend about whether he has ever really cared. "I don't want to care. If I care about things, it'll just be worse, it'll just be another thing to think about. It's less painful if I don't care."

Up to this point, Clay has travelled among the book's cast of dead-eyed rich kids snorting too much cocaine, popping valium, watching snuff movies, having passionless sex, remaining monosyllabic and inscrutable until the end. In this confessional moment that defies logic and all it means to be human, the young Clay concludes it is better not to feel, or even to think, in order to exist in his toxic universe of consumerist overload.

Ellis, himself a 20-year-old son of privilege at the time he wrote Less Than Zero, now returns to these characters' lives with his seventh novel. Imperial Bedrooms is written in the same two-dimensional style and syntax, as deliberately flat as one of Andy Warhol's "Marilyn" silkscreens, but this time structured as a postmodern noir. Clay, who, like Ellis, is now in his forties, is a Hollywood screenwriter returning to the LA of his youth and the characters who inhabited it including Blair, his ex-girlfriend who is now married, and Julian, his friend whose body is found mutilated at the beginning of this novel.

Clay has, true to his word, assiduously stuck to thinking and feeling as little as possible. He indulges in transactional sex with actresses by promising them auditions and fends off the enemy of emotion with regular doses of alcohol and sedatives such as ambien, living with a kind of psychic "locked-in" syndrome. The central mystery - Julian's death and a spate of other torture-murders – unleashes the usual tropes of noir fiction; mysterious SUVs creeping along Clay's driveway, a sense of being watched, a love triangle, a femme fatale (Rain, an actress sleeping with Clay in exchange for a "call-back").

Some of these tropes appear as ironic as the self-parodying humour in the genre of Hollywood's "knowing" scary movies – Clay is sent recurring text messages that read "I'm watching you" – yet they do create a genuine sense of dread and paranoia. The dread, in Clay's case, might be more metaphysical than real, a fear of his own subjectivity or the dread of being called up and stalked by his guilty conscience.

Noir elements that might seem trite in themselves are inverted cleverly; aspects of the novel offer a play on Billy Wilder's noir classic, Sunset Boulevard, also set in Hollywood. Ellis reverses the film's central relationship between the older, silent movie actress and the struggling young screenwriter - her kept man. Ellis turns this on its head with Clay and Rain's relationship and throws in a passing reference to an imagined body found floating in a swimming pool, invoking the opening scene of Wilder's film.

In the end, Ellis makes clear his noir is employed as a circular strategy, as meaningless as the plot and characters themselves. "This isn't a script," Julian tells Clay. "It's not going to add up. Not everything's going to come together in the third act."

Nothing adds up, and deliberately so. Just as in the case of Patrick Bateman's unreliable narration in American Psycho, Ellis's third novel, which conflates reality (as New York banker) and fantasy (as serial killer), the noir element here creates a questionable reality. Is Clay really being followed or is he being dogged by a guilty conscience for crimes committed, even when they are crimes of inaction?

In Less Than Zero, Clay watches as a tormented Julian has sex with an older man for money; he runs into an alleyway with his friends to stare into the eyes of a young man, only recently murdered with freshly shed blood not yet congealed on his face; he watches the rape of a drugged 12-year-old girl, handcuffed to the bedpost, tortured for kicks. He observes these heinous acts without any intervention or moral protest, yet justifies it in his mind by insisting he is not as thrilled by the voyeurism as his more "active" friends. Now, 25 years on, his passivity has hardened into something far more culpable, and nefarious.

There is a final scene in Imperial Bedrooms of unremitting torture that is either enacted by Clay on two beautiful teenagers who are bought and systematically abused, or imagined by him as a fantasy. In showing Clay's graduation from a passively colluding observer to active perpetrator now, a man who either indulges in torture or fantasises about it, Ellis suggests that evil begins with torpor - induced by ambien and valium – or by emotional disengagement. One character expresses this descent into evil: "Who knows why people do the things they do... You discover things about yourself you never thought possible."

Often, descriptions of Clay's LA verge on a Brave New World-style fantasy, where the "command economy" now manifests as rampant, late-capitalist consumerism, where ambien is the new soma and humans are zombies: one character's face is "unnaturally smooth, redone in such a way that the eyes are shocked open with perpetual surprise; it's a face mimicking a face, and it looks agonized."

Ellis, a self-confessed moralist, has suggested that far from offering a celebration of evil and of nihilism, he is presenting an examination of it. The nascent narcissist of Less Than Zero has lost all ability to empathise, switched off his humanity, and is now left in a "dead end". In that, it is a deeply pessimistic presentation of human nature as assailable, and in Clay's case, incapable of transformation; but also, perhaps, an unflinching study of evil.