Until very recently, cinema and television completely shunned the postmodernist authors known for their gargantuan and elaborate takes on the Great American Novel. Works such as Thomas Pynchon’s Gravity’s Rainbow, Don DeLillo’s Underworld and David Foster Wallace’s Infinite Jest were evidently too monstrous and opaque, and had too many strands, characters and locations, to be processed; but the writers’ shorter and less complicated novels (Pynchon’s The Crying of Lot 49, for example, or DeLillo’s White Noise) were also overlooked – their idiosyncratic, unpitchable stories were apparently not ones even arthouse directors wanted to tell.

It was after Foster Wallace’s death in 2008, and with the near-contemporaries DeLillo and Pynchon entering their late 70s, that the first tentative screen adaptations started to appear. A movie of the younger novelist’s short story collection Brief Interviews premiered at Sundance in 2009. David Cronenberg’s version of DeLillo’s novella Cosmopolis was released in 2012, the same year that The Simpsons reworked a Foster Wallace non-fiction account of a cruise. And now Pynchon’s 2009 crime novel Inherent Vice – a mixture of noir and narcotics helpfully centred, like Cosmopolis, on one person, Californian private detective Doc Sportello – has become the first of his works to be filmed.

In Pynchon’s case, there is a particular melancholy to the long wait, since few postwar authors’ novels are so saturated with cinema. His books are not only obviously produced by an obsessive film buff (as evidenced by one wry recurring trick, the dates in brackets that follow even citations of celluloid ephemera), they often seem to want to be movies, as shown by another signature device, the way his protagonists – from the 1890s European spies and 1950s New Yorkers in the interwoven narratives of his debut, V. in 1963, all the way to Inherent Vice and Bleeding Edge in 2013 – break anti-naturalistically into song like characters in musicals.

Movie envy is especially marked in the vast, V2 rocket-fixated Gravity’s Rainbow (1973), set in London and Germany in 1944-45, and where Pynchon displays equal familiarity with German expressionist cinema, the oeuvre of Leni Riefenstahl and a host of 30s and 40s Hollywood films, among them The Wizard of Oz and Tod Browning’s Dracula and Freaks. Forty years later in Bleeding Edge, located in Manhattan before and after 9/11, the nods to classic foreign films have gone - reflecting a wider shift away from referencing, and trying to rival, high points of highbrow culture in his later novels - , but its heroine Maxine Tarnow and her family are just as addicted to screen fiction as their earlier counterparts and it continues (if only because they still imitate characters played by stars such as Grace Kelly or even Jennifer Aniston) to shape lives and destinies, often comically but sometimes sinisterly.

Inherent Vice is set in 1970 in Gordita Beach, a fictional, hippie-friendly Los Angeles suburb based on Manhattan Beach and so less than 20 miles from Hollywood. It begins with a film actor, Sportello’s ex-girlfriend Shasta Fay Hepworth, initiating the first of his many interlocking investigations by asking him to find her missing lover, construction tycoon Mickey Wolfmann. Popping up throughout is swaggering, outlandish LAPD detective “Bigfoot” Bjornsen, a self-styled “renaissance cop”, who also acts in commercials and television police shows and dreams of writing and starring in a TV movie about one of his own crime-busting feats.

Sportello himself has almost as prodigious an appetite for cinema as he does for drugs, and an encyclopedic knowledge of the two fields; in his regular sessions watching late-night films on TV while smoking joints, the two ambiguous vehicles for fantasy (both mind-liberating but potentially mind-warping) come together. Hollywood has primarily shaped him, however, by providing him with a role model: the stoned sleuth was improbably inspired to become a detective, we’re (oddly) repeatedly told, by the flinty, combative 40s star John Garfield, whom he inferrably sees as an authentic, working-class alternative to the posh faux tough guy Humphrey Bogart.

That its hero idolises a by now almost-forgotten movie idol is not reflected in Paul Thomas Anderson’s screenplay, but that’s one of only a handful of respects in which his adaptation is unfaithful to the text. With a cast led by Joaquin Phoenix and including Josh Brolin as Bjornsen, Benicio del Toro as a likable lawyer, Owen Wilson as a musician turned informer and Reese Witherspoon as a deputy DA who is Sportello’s occasional squeeze, the film follows the novel’s plot devotedly; even its most perplexing feature, the Golden Fang – at once a real ship and a suspected conspiracy the private eye uncovers that seems to encompass heroin trafficking, the sex trade, property development, unscrupulous psychiatrists and dentists, rogue elements in the LAPD and FBI, and neo-Nazis – is reproduced in all its bemusing detail (Anderson apparently told his cast to see it as a metaphor, “a catchall for everybody’s paranoia”).

As Sportello seeks to rescue Wilson’s sax player from the Golden Fang’s clutches as well as trace Wolfmann, Pynchon’s exotically named Californian oddballs, screwball comic dialogue and zany plot twists - even every move in the book’s climactic fight scene - are lovingly transposed to the screen; though the film’s second half all but edits out a third missing person investigation that takes Doc to Las Vegas, and reworks the ending.

Strikingly, Anderson’s most obvious deviation from Pynchon reflects respect for him rather than criticism, and awareness of what usually gets lost when novels are dramatised: he promotes a minor character, the detective’s mystical ex-assistant Sortilege (played by Joanna Newsom) to narrator, and her sporadic voiceovers allow some of Inherent Vice’s descriptive passages and sociopolitical musings to find a place in the film.

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This, then, is a fanboy project, and in interviews Anderson has stressed his desire to do equal justice to Pynchon’s stream of gags and his dark vision of a counterculture being repressed or “ripped off” by a conspiracy of the powerful: in making the film he was “trying to be a surrogate for Pynchon’s concern for the American fate”. According to Phoenix, author and director were in regular contact by phone during production.

Linked by their nostalgia for the 60s and fascination with authority figures, the movie maker and the movie buff seem counter-intuitively to have acted as a beneficial brake on each other. After the sometimes enigmatic narratives of There Will Be Blood and The Master, Anderson is forced to be more formulaic by the novelist’s droll homage to Californian detective fiction, as well as to remember that he once did comedy, too, in Boogie Nights. He pares back Pynchon’s excesses, and by doing so reveals Inherent Vice to be surprisingly straightforward – amid all the jokes and smokes, Sportello rescues one missing man and finds the other, nails some villains and fools others, eludes bad cops and FBI agents, and sort of gets the girl. He really is a John Garfield-like driven do-gooder after all, albeit disguised as a pothead slacker.

For Pynchon, this is a deluxe debut on film – with a multiple Oscar-winning adapter-director, period-evocative 35mm visuals by Oscar-winning cinematographer Robert Elswit and a score by Radiohead’s Jonny Greenwood – and another step in a recent, limited process of warily opening up and releasing control. He still gives no interviews and bans photos, but saying yes to Anderson follows appearances (with a bag on his head) on The Simpsons, voicing a trailer when Inherent Vice was published, and including clearly autobiographical elements in Bleeding Edge.

With its linear plot, unliterary prose and freewheeling humour, Inherent Vice is early Pynchon condensed, simplified and sweetened - and usefully for Anderson, confined to a single community. Less amenable to adaptation are his big historical novels in which empires clash and the malign political or military-industrial conspiracies stretch across oceans, or back across centuries. The Crying of Lot 49 (also set in California and modelled on Chandler, also very funny) might tempt other directors now Anderson has shown adapting him can work, but don’t expect to see Gravity’s Rainbow on screen any time soon.