Don't panic — not just yet, anyway. "The Hitchhiker's Guide to the Galaxy," the long-awaited screen version of Douglas Adams' cult novel of interplanetary discovery, is here, and while it's undeniably a mess, it's a zippy, lighthearted, enjoyable ride. Purists may miss their favorite bits or raise eyebrows over the somewhat altered ending, but the book's goofball — and very British — humor survives intact.

Adams, who died in 2001, based the book on his own BBC radio play, which in turn became a wildly popular series of novels (and, along the way, a television show). Before his death, he wrote two drafts of a movie screenplay, which was later revised by Karey Kirkpatrick ("Chicken Run"). Video/commercial director Garth Jennings signed on, a quirky cast was selected, and off they all went, knowing that science-fiction fans were watching their every move.

And will those fans be happy? Well, speaking not as a rabid fan but as someone who just read the book the other day (and was pleasantly surprised by how funny it was), I thought the book and movie shared a nicely whacked-out, random quality — an episodic string of things happening, some funnier than others. The movie often doesn't seem to be going anyplace in particular, but the wit, the visual imagination and the likability of the actors keep this often unwieldy ship afloat.

Regular-guy Arthur Dent (Martin Freeman, of the BBC TV series "The Office") wakes up one morning to find his house slated for demolition to create a freeway bypass. Turns out, this doesn't matter — the world's about to end anyway, and Arthur, a puffy-faced everyman in pajamas and green terrycloth bathrobe, is whisked away on an intergalactic journey, guided by the electronic book "The Hitchhiker's Guide to the Galaxy." He learns the importance of always having a towel; discovers the meaning of life (42); meets such creatures as Babelfish and Vogons (beware of their poetry!); and finds love, in a development embellished for the movie, presumably on the theory that it's not really a movie unless two people kiss.

All this is plummily narrated by Stephen Fry, interjected with animated tidbits tossed in like nuts in a salad, and populated with some irresistible characters.

Alan Rickman's mournful voice is a perfect match for the robot Marvin (physically portrayed by Warwick Davis), who waddles along miserably, making predictions ("This will all end in tears") and observations ("I've been talking to the ship's computer. It hates me.") Sam Rockwell, in flaxen curls, turns galaxy president Zaphod Beeblebrox into a combination rock star, surfer dude and television evangelist. Mos Def, an underrated actor (he was terrific in "The Woodsman"), brings warmth and oddball humor to alien "Guide" researcher Ford Prefect — he does a very funny fake hug — but the movie too often seems to forget about him.

A redheaded John Malkovich pops in as intergalactic missionary Humma Kavula, who leads a cult awaiting the return of a large handkerchief. (Don't bother scanning the novel for this character; Adams created him for the film.) Bill Nighy, charmingly exasperated, plays planet construction engineer Slartibartfast. And Zooey Deschanel, she of the endearingly loopy speech patterns, is Arthur's love interest, Trillian (formerly Tricia).

It's clear, watching the movie, that Jennings' forte is short film; his "Hitchhiker's Guide" doesn't really hold together as one full-length movie and it's sometimes so choppy you wonder what was lost during the editing process. But for all its faults, the film is genuine fun.

A day later, I'm still humming the movie's theme song, the title of which will resonate with Adams fans: "So Long, and Thanks for All the Fish."

Moira Macdonald: 206-464-2725 or mmacdonald@seattletimes.com