Ice, Mud and Blood: Lessons from Climates Past (Macmillan Science)
If you want just one book, not too thick or too technical, that will give you the intellectual tools to at least understand what the climate change experts are talking about, this is the one. I recommend bringing it to the beach and reading it there -- you'll appreciate the rising tide and the ocean beaches a little more, and perhaps regard them with a little more respectful dread. --Pharyngula, July 2, 2008