Books that changed the way I think about the universe...er..."'verse""
Cosmos, Demon Haunted World, & Shadows of Forgotten Ancestors, by Sagan.
Really dated, but The Ascent of Man by Jacob Bronowski, especially the chapter entitled "Knowledge or Certainty?"
The Selfish Gene & The Blind Watchmaker by Richard Dawkins
The Star Thrower by Loren Eiseley...anything by Eiseley, for that matter...