Can anybody recommend a good book about endgames?  Not one that is just filled with puzzles.  Though puzzles are good, I want to learn endgame theory and tactics, and find that puzzles on their own don't do it for me.  I'm looking for a book that explains and teaches the theory behind various kinds of endgames.

Any suggestions?

This puzzle book also teaches:

http://www.amazon.co.uk/Test-Endgame-Ability-Popular-Chess/dp/0713455675

At the very least an excellent adjunct to the books others will list here.

Silman's Complete Endgame Course seems like it's the standard recommendation these days, and it's a great book.

Here's one that a little different and may be more of the type of book you're looking for:  101 Chess Endgame Tips by Steve Giddins.  Here's a link to a sample http://www.gambitbooks.com/pdfs/662Samp.pdf

Silman's book is a great alternative!