The folks at O'Reilly recently published this gem !

From the book description:

This book is a comprehensive guide to the tips, techniques, secrets, standards, and methods of website optimization. From increasing site traffic to maximizing leads, from revving up responsiveness to increasing navigability, from prospect retention to closing more sales, the world of 21st century website optimization is explored, exemplified and explained.

Though I've just started readying it I'm already convinced it's a must have !

[ Click Here to get your copy ! ]