If you’re one of those who fondly recalls spending the ’60s luxuriating in a pleasantly disorienting haze, well, consider "Inherent Vice" a reunion of sorts. You’ll fit right in.

If, on the other hand, your sensibility is better suited to a different era, you may have a tougher time with Paul Thomas Anderson’s freewheeling, trippy, undeniably uneven adaptation of the 2009 Thomas Pynchon novel. It’ll either exhilarate or exasperate you, depending on how much you crave logic, definitive answers, and clear plotlines — all of which are in as short supply as visible skin on Joaquin Phoenix’s cheeks under those bushy mutton-chop sideburns.

Despite the film’s frustrations, it must be acknowledged that Anderson — a master of the multi-strand, multi-character, multi-meaning plot — is the perfect director to adapt Pynchon, in terms of both craft and spirit. As to be expected, he’s amassed a wholly entertaining cast, ably led by Phoenix as Doc Sportello, a beach-loving, weed-imbibing private eye who gets enmeshed in a bizarre whodunit that unfolds like an onion laced with LSD.

The action takes place in 1970, to be precise, just as the ’60s are about to morph into something different — not that Sportello seems all too conscious of that. He lives and works, but mostly smokes pot, in fictional Gordita Beach, where, one day, his old girlfriend pops by. Shasta Fay Hepworth (newcomer Katherine Waterston, winsome and appealing) tells Doc about her current flame, real estate magnate Mickey Wolfmann (Eric Roberts). Seems the rich guy’s icy British wife — and her boyfriend — are plotting to kidnap Mickey and maybe toss him into a loony bin, with her help. What should she do?

And then poor Mickey and Shasta disappear.

Meanwhile, there’s Hope Harlingen (Jena Malone), a former addict with an impressive set of false teeth, trying to track down her missing husband, Coy, a saxophone player who may or may not be dead. Turns out that Coy (Owen Wilson, right at home here with his languid surfer speech) was up to some crazy undercover stuff.

But back to Shasta, whom Doc still pines for: Starting to investigate her case, he visits an erotic massage parlor, gets knocked out and winds up next to a corpse.

Thankfully that brings Doc face to face with Lt. Det. Christian "Bigfoot" Bjornsen — and we say thankfully because this idiosyncratic LAPD detective with a flat-top hairdo is played by Josh Brolin, who squeezes every ounce of high-octane comedy out of the role. Bigfoot sucks suggestively on chocolate-covered bananas, bashes in doors when he could just open them, moonlights on TV (he’s an extra on "Adam-12"), and barks out orders for pancakes in a hilariously distinctive manner.

What’s next? Wrong question: Unless you’ve read the book, and maybe even if you have, the plot eventually becomes impossible to sort through — at least if you’re also trying to simply enjoy meeting the assortment of unusual types flitting through. They include Reese Witherspoon as Deputy DA Penny Kimball, all buttoned up until she’s not, and Martin Short, bringing his manic comedic skills to the role of Rudy Blatnoyd, D.D.S. — a horndog, cocaine-loving dentist. There’s also a terrific turn by theater actor Jefferson Mays as a menacing doctor.

Cinematographer Robert Elswit nicely captures a surf-culture vibe (he recently explored a darker, grittier, more current Los Angeles in "Nightcrawler"). The film is narrated by a mysteriously spiritual character named Sortilege, Doc’s ex-assistant (singer-songwriter Joanna Newsom.) But does she put it all together for us? Nah. As the ending credits roll, it’s best to merely focus on their lovely neon colors, and not try to recall precisely what just happened.

After all, they say that if you can remember the ’60s, then you weren’t really there.