It has to be Hitchhikers Guide to the Galaxy for me. Not only is the book itself fantastically funny, but it was also a book I would sit and read with my dad. We would each take it turns to read a page, and this remains one of my most cherished memories of childhood. It's a world I can still picture perfectly, even though it has been a few years since I revisited it.
I would say it's a must read if your into quirky, funny sci-fi stories.
