<p>The movie is based on the first novel in the "trilogy" of five. <em>shakes head, laughing</em> Don't worry about the movie spoiling the books. The movie is a giant recycling bin of random, brilliant, ideas, haphazardly strung together. It's much like the books in that respect. So, if you haven't read the first book, you will be utterly lost. The movie will be maddening and, most likely, you'll walk out halfway through. There are a few superficial nods to the other books, but that's all. Don't worry about it. Douglass Adams could never keep the characters and plotlines straight, himself. He changed them every chance he got (in each radio show, the TV series, the first movie, the game, and his drafts of the new movie's screenplay).</p>
<p>He added a character in the movie just because! (And John Malkovich plays it, which gives me no end of giggles after comparing that to his stint in Being John Malkovich.)</p>
<p>All of the reviews (and this is from friends, too) say that if you're not familiar with the book, you will hate the movie/be lost. So read it. </p>
<p>The Hitchhiker's Guide to the Galaxy is the name of the first book. It is also the name of the "trilogy in five parts" that includes (as well as h2g2) Restaurant at the End of the Universe; Life, the Universe and Everything; So Long and Thanks For All The Fish; and Mostly Harmless. The movie is essentially based (though loosely) on book #1, though as Nom says it includes nods to a few of the other books. It also has a few nods to the Douglas Adams subculture (including three appearances of his head!).</p>
<p>It is destined to be a cult film. I say alas to this, but in reality it makes me happy. The critic reviews really bothered me; it seemed to me like the people who hated it didn't get it (and not just because they hadn't read the books). A George W. Bush parody? Egh. Just enjoy the freaking movie for what it is -- entertainment gold without reliance on special effects.</p>