Steve Krug, Don’t Make Me Think: A Common Sense Approach to Web Usability, 2nd ed. (Berkeley, CA: New Riders).
Krug’s book on web design is terrific. It’s a nice edition in full colour with lots of illustrations. Whether you’re a novice designer trying to build your first web site or a seasoned veteran, Krug’s “Laws of Usability” are easy to understand and remember. He discusses the fundamental design elements every site should have and why (with concrete, full-colour examples), spends some time talking about usability testing, and even provides a generous “Further Reading” section. Even if the only website you manage is your own personal one, this book will help you get the most out of it. I highly recommend it!
UPDATE 2016: Read the latest edition and still think this is a must-have book in a UX library.