Why you shouldn't read the books
Everybody knows the hitchhiker's Guide To The Galaxy. It's a famous book series, you may have seen the most recent movie, but did you know it was originally not a book, but a radio show which first aired on the BBC in 1978?
I know very few people who have actually listened to the show, but to me it's definitely the best way to enjoy the Hitchhiker's Guide To The Galaxy. It's pretty difficult to find a place where you can download the mp3 version of the show, even if you're willing to pay for it. The BBC website doesn't help much, although it has this antique Hitchhiker's Guide To The Galaxy microsite. You can order the CD version from Amazon. Otherwise, you can just Google it, the first result at this time is a website ofering the MP3 version for free (disclaimer: I have no idea whether this source is legal, download at your own risk and buy it from somewhere else if you have any doubt).
As a bonus, here's the late Douglas Adams explaining how he came up with the idea for The Hitchhiker's Guide To The Galaxy.