The Hitchhiker's series was so delightfully... random. It's undoubtedly the most umpredictable series of works I've read. As for the movie, I would forgive almost anything for two reasons: 1) the way they depicted the Infinite Improbability drive; and 2) Alan Rickman doing the voice of Marvin. No one does peevish like Rickman.
I very much enjoy the trilogy and have re-read a few times over the years. Very fun stuff! Remember the frustrating computer game? Did not like the movie one bit. Have found the BBC tv and radio show enjoyable, though.
I enjoyed the radio shows, they were exactly the same as the books really, so that was good...but I hated the movie. In and of itself it was well done...but to me, after reading through the Hitchhiker's Guide 5 or 6 times and knowing pretty much the whole plot line back to front (not word for word mind you. Terrible memory I have) I just found the movie a bit lacking, missing some of the best elements from the book. Douglas Adams was a brilliant author, not just limited to Hitchhiker's Guide trilogy (in 5 parts) but with his other assorted works. Brilliant.
Just wanted to make sure everybody knows that another book is coming out!! It's being written by Eoin Colfer, the guy who wrote Artemis Fowl. http://news.bbc.co.uk/1/hi/entertainment/7619828.stm I adored all the books, the BBC series AND the modern movie (even though it wasn't 100% accurate, and not as good as either the books or the BBC series)