Asimov's New Guide to Science
Cover scans
Click a cover for a larger version.
Synopsis
This is a thick door-stopper of a book, dealing with all of science (and the history of science in general). It's divided into two major parts, The Physical Sciences and The Biological Sciences.
Review
Asimov wrote very well fiction, but I think non-fiction is where he shines, and this book is no exception. Go buy it, and get an overview of the vast fields of science!