I might be stating the obvious, but:
The Hichhiker's Guide to the Galaxy by Douglas Adams!
Amazingly funny book. Also plenty of extra stuff around that book, like bbc radio drama's. A must read. I bet many of you already read it.
And ofcourse Terry Pratchett's Diskworld series. Sadly, i'm almost done reading those. Especially the later ones are very witty, a breeze to read and ful of hilarious moments, satire and good storytelling. Nice and light reading.
When younger, aside from the mandatory Lord of the Rings and various other books, i remember enjoying The Wheel of Time by 'Robert Jordan'. But looking back, those books did get slightly boring after part 10. And i also remember reading stuff by Eddings i enjoyed. But ignore that. Read the Hichhiker's Guide if you haven't! It's a classic.