If you're trying to figure out what to buy yourself with the gift card you got this holiday season, let me recommend David Pogue's Mac OS X: The Missing Manual, Leopard Edition. I was fortunate to get a copy of it for Christmas this year (thanks, sweetie!) and it's 866 pages of sweet, Leopard-y goodness.
The book is divided into six sections that cover just about every conceivable thing you could ever want to know about the OS. It takes a look at how to maneuver around the desktop, how to use the native apps to their fullest potential, what to do with once your online with your Mac, and everything in between.
If you already know your way around OS X, this manual is a terrific reference tool for looking up obscure things you don't do very often, like tweaking onscreen colors to mimic a Windows PC monitor. At the other end of the spectrum, if you're a switcher there are roughly seven trazillion tips and tricks to help you learn how to get the most out of your new operating system.
Pogue's writing style is upbeat, easy to understand, and sometimes downright hilarious. The book is well laid-out and progresses fairly intuitively, although the editor seems to have gone a little crazy with the headings, sub-headings, and sub-sub-headings on many of the pages. Also, while I'm sure Pogue touches on all 300 of Leopard's new features, it's not always immediately clear which features he's describing are different from the previous version, Tiger.
Despite these minor shortcomings, I love this book and think it's a great addition to any Mac users bookshelf. This manual is one you don't want to miss.