The comic is TOTALLY different, but I still (suprisingly) love the movie!
I was disappointed that Steve B's role from the movie wasn't as broad in the comic book (I saw the movie first, which was dumb of me...), but you get over it. The story line is...the same, but different, like the trip that they take, and that Enid drives the herse and all that --that doesn't happen in the movie. You really have to watch the movie to see the differences. Both are fantastic, and I totally reccomend watching the movie. If you understood the comic book, then you should understand the movie, but I will concur with ampersandwitch and say that it might take a few viewings before you "get it"...