If you're looking for phliosophy then start with "The Minds Eye". The book is a collection of papers, essays and stories all dealing with cogniscience and duality (is the mind and body connected or seperate). I can't remember who is the 'author'/editor but every big book store I've been in has a copy.
My personal, all time favourite book is "The Selfish Gene", by Richard Dawkins. This is a book about evolution and associated topics. Why would a book about evolution be my favourite you ask? This book allowed me to become an athiest. The problem with being athiest is you have to develop on you own all those things that religion normally hands you. This book was where I started.
"Gun, Germs & Steel", by... I can't remember the author (I think it's Jerod Diamond, or something like that) and my friends has my copy, but the book is well known. It was on the New York Times best seller list for quite a while. It traces the development of the human species over the past few thousand years. Very accessable to all readers.
For philosophy... I'd read Heigel (not too sure if I spelled that right, it's pronounced Hegal... sorry but it's been a while since I've read his stuff). Marxs and many others developed their theories based on his work. His dialectic/synthesis process is a very good starting point.
Finally... anything by Terry Prachet, but especially "Bad Omens". "Bad Omens" is one of the funniest books I've ever read, hands down. It's all about the end of the world. Really, really funny stuff with dry British wit.