Douglas Adams described his book - the first of the multi-media franchise - as "a long beginning and an end." And true to his phrase, for better and worse, the film of "The Hitchhiker's Guide to the Galaxy" is exactly that as well. It begins with one of the most delicious openings I can recall in film: Earth is about to be destroyed to make way for a highway bypass. The world's dolphins ("the second smartest species on earth," as the narrator reminds us - humans being the third) sing a wonderful Broadway show tune about having to leave, but "thanks for all the fish." They do a synchronized ballet to the music and then take off for, well, someplace that's not about to be obliterated.

And it begins again with everyman Arthur Dent (Martin Freeman, of the British television series "The Office") being airlifted off the earth by his pal, the alien Ford Prefect (Mos Def), while mourning his lost chance at connecting with Trillian, the girl he met once (Zooey Deschanel). And it carries Arthur and Ford along their hitchhiker's serendipitous path through the universe, aided occasionally by the Guide itself ("Don't Panic" is written on the lid) as they meet the President of the universe - a ceremonial office - Zaphod Beeblebrox (Sam Rockwell) who signed the destruction order thinking it was a request for an autograph.

They meet the Vogons, powerful enough to do evil things, mostly through their bad poetry. And so on, with Ford's magic thumb taking them from place to place. The film is a lovely idea, but by being too faithful to the episodic concept of the book, radio and television series, it loses momentum. To borrow a hated scriptwriter's phrase, there's no throughline in the film. One sequence does not lead to another, which does not develop the previous one into something richer, deeper, or even more fun. The film was written by Karey Kirkpatrick with co-screenplay credit given to Douglas Adams, and directed by Garth Jennings, one half of a British team that calls itself Hammer and Tongs (the other half is producer Nick Goldsmith). Their previous work has been in music videos, and it shows, also for better and worse, in "The Hitchhiker's Guide to the Galaxy," as both the frequently striking images and yet an inability to hold us for more than a few minutes at a time.

Another problem here is Sam Rockwell, who perhaps in an attempt to give himself a stronger presence than he had as the requisite sailor who (like Kenny in "South Park") was always killed in "Galaxy Quest," has gone out of control with a bad impersonation of George W. Bush. Had it been a good one it would have been classic, but his mumbles and chewed-up lines here don't mesh with anything else in the movie and just stop us from enjoying the story. More than that, the film itself is an uneasy attempt at blending British understatement with American directness; Mos Def and Martin Freeman are not a match made in heaven. In fact they seem to be located in two different films at the same time. I think in an attempt to make more of the story than was there, the film ends up being less instead. I do love the dolphins, though.