Thomas Pynchon doesn’t usually write this quickly. His books, which tend to be extended affairs — “Against the Day” (2006) sprawled over 1,085 pages — usually come one per decade, and they’re not exactly beach-read material. “Inherent Vice,” however, follows its predecessor into print a mere three years later, and it bears testament to a less belabored writing process: with fewer than 400 pages of mostly lucid narrative, it may be the most accessible book Pynchon has ever written.

“Vice” is pegged as a detective novel, but its most obvious antecedent is “The Crying of Lot 49.” Like Pynchon’s 1966 caper, “Inherent Vice” depicts LSD use and references 1960s pop culture and rock music — in this case focusing on the surfer slash hippie slash beach bum surf-rock subculture of the fictional LA satellite Gordita Beach — and both books revolve around ill-fated California real estate moguls entangled in what may or may not be a sinister conspiracy.

Four decades after “The Crying of Lot 49,” though, Pynchon’s vision of California has crystallized into something more mythological. Doc, the novel’s affable if somewhat jaded hero, belongs to a kind of Gnostic tribe of surfers and seers; the residents of Gordita Beach are privy to metaphysical truths and wavelengths unknown to the Nixonite, commercially-minded public (usually referred to as “flatlanders,” or, my personal favorite, “quadrilaterals.”) Doc is a private investigator well-acquainted with the seedier side of Los Angeles and its environs, but that’s where the similarities between him and Phillip Marlowe end. Unlike Raymond Chandler’s iconic, hard-drinking P.I., Doc prefers a joint, and his professional approach is accordingly laid back. Once, we are told, Doc lit up and fell asleep on the roof of a house while monitoring a cheating wife, only to wake up to police sirens and the aftermath of a double homicide.

Obedient to the conventions of the genre, however, Doc rises to the occasion when an important case is at stake, and adheres to a loose code of chivalry that sets him apart from the crooked cops of the LAPD. The case in question concerns the disappearance of Mickey Wolffmann, billionaire property developer and current boyfriend of Doc’s “ex-old-lady” Shasta Fey. Much of the book unfolds in what is, in retrospect, a predictable fashion, delivering exactly what you would expect from a detective novel written by Thomas Pynchon. There are characters with ridiculous names (Sauncho Smilax, Bigfoot Bjornsen), rock lyrics by imaginary bands with ridiculous names (Spotted Dick, Meatball Flag) and a few car chases fueled more by weed-induced paranoia than any imminent danger. Hints of a vast conspiracy spiral outward, eventually signifying little more than the acid-trip interconnectedness of everything.

It would all be a little much if it weren’t for the fact that Doc is such an enjoyable protagonist. His repartee ranges from chuckle-worthy to lame (“Can I ask you something?” “As long as it’s not the capital of South Dakota.”) but his good humor — cynical, bemused, but inclined to see the best in people — is contagious. Doc is convincingly three-dimensional, a welcome surprise from an author not especially well-known for creating characters with rich emotional lives. Likewise, the slacker paradise of Gordita Beach is warmly rendered, and an extended detour into Las Vegas around the halfway point of the book feels stale by comparison.

Sunsets figure prominently in “Inherent Vice,” both the “daily occurrence” and the Boulevard. Pynchon deliberately avoids mentioning the exact year — post-Manson, pre-Watergate is a safe bet — but it’s all too clear that the sun is setting on the Psychedelic Sixties. In the author’s sentimental interpretation, this represents the passing of a noble experiment and the triumph of a social order increasingly dominated by manipulative, inhumane sources of authority. Whether he offers an accurate representation of a time and place or a myth thereof, the fact remains that there is real feeling in what he writes. It seems unlikely that Pynchon will give us another straight detective novel in the vein of “Inherent Vice,” but I wish he would — perhaps in time for next summer, to be read on the beach.