Of all the witty, irreverent, sublimely blasphemous ideas put forth in Douglas Adams’ “The Hitchhiker's Guide to the Galaxy,” one stands out as a personal favorite: A hokey intergalactic religion that defines creation as the moment when God let forth a mighty, cataclysmic sneeze, leaving is followers to await the coming of “the Great Handkerchief.” Amen.

Such is the genius of the “Hitchhiker” books, a “trilogy in five parts,” as Adams snarkily referred to them. Unique among science-fiction literature, the cosmos-trotting adventures of intrepid Englishman Arthur Dent were devised to make the foibles of man seem comically, comfortingly irrelevant — a quality shared by most major religions. For all his cheekiness, Adams was dealing in secular Scripture.

First-time director Garth Jennings makes a noble effort to translate the word of Adams in the long-awaited big-screen version of “Guide,” with wild and wildly uneven results. Purists already know the story of Dent (Martin Freeman from the BBC's “The Office”), the feckless bachelor whose home is demolished to make way for a freeway bypass just as the Earth is obliterated by aliens for travel convenience. Luckily, Dent's best friend, Ford Prefect (Mos Def of “The Woodsman”), is actually an extraterrestrial journalist compiling information for something called “The Hitchhiker's Guide to the Galaxy.” Ford and Dent hop the nearest starship and escape obliteration (an unimpressive spectacle, as it turns out — George Lucas could probably conjure better special effects on his Palm Pilot).

Fortunately, the movie — co-scripted by Adams and Karey Kirkpatrick — boasts more raw creative daring than a dozen “Star Wars” prequels. Ford and Dent suffer the indignity of bad Vogon poetry (the “third-worst poetry in the galaxy,” the Guide's computer narrator soberly informs us), make friends with a manic-depressive robot (Alan Rickman) and join forces with Zaphod Beeblebrox (Sam Rockwell from “Confessions of a Dangerous Mind”), the two-headed president of the galaxy, on a mission to surmise life's great question (we already know the answer — it's “42”).

As it happens, Beeblebrox is racing around the galaxy with Dent's former would-be girlfriend (Zooey Deschanel from “Elf”). Improbable? Well, yeah, but improbability powers their spaceship.

Jennings bombards us with every possible vagary from Adams’ novel, and even for fans, it will be a bit numbing. “Guide,” a truly effortless read, presents a cumbersome viewing challenge.

Still, with a cast this talented (Def is hilariously slick; Rockwell, maniacal) and material this rich (“Men in Black” can trace its sci-fi comedy genealogy back to Adams’ innovations), audiences should savor the experience. “Guide” is essentially a love story about the last two Earthlings in the galaxy, and who could deny the romance in that?