Normally, I don't have a lot of problems making decisions like this, but I've changed my mind 3 times about which book will get my top vote in this year's Jolt Awards for Technical Books. This is a very, very good set of books:
Books (Technical)
Code Quality (Addison-Wesley) by Diomidis Spinellis
How to Break Web Software (Addison-Wesley) by M. Andrews, J. Whittaker
Java Concurrency in Practice (Addison-Wesley) by Brian Goetz et al
Rails Recipes (Pragmatic Bookshelf) by Chad Fowler
Refactoring Databases (Addison-Wesley) by Scott W. Ambler and P. J. Sadalage
Head First Object-Oriented Analysis and Design (O'Reilly) by B. McLaughlin, G. Pollice and D. West
Ruby Cookbook (O'Reilly) by Lucas Carlson and Leonard Richardson
CSS: The Missing Manual (O'Reilly) by David Sawyer McFarland