SharePoint 2007: The Definitive Guide, by James Pyles, Christopher Buechler, et al. O'Reilly, ISBN 0596529589.
This book's very broad in its coverage of SharePoint 2007 and sacrifices depth for that breadth. While there are several chapters on development-related topics, development isn't the book's forte. Rather, the book's really targeted to giving a lot of background and foundational information for folks wanting to implement Windows SharePoint Services (WSS) or Microsoft Office SharePoint Server (MOSS).
11 different contributors make some parts of the book difficult with their wide range of voices, and there are a number of clunky parts and some flat-out errors. (One minor example: A diagram of server topology switched the labels between the web front ends and application servers.)
Those nits aside, the book's well done and a solid resource for folks moving in to the WSS/MOSS arena. The sections on architecture, installation, and topology are all fine bits for discovering the broad strokes. The remaining chapters hit functional jobs like site design, managing workspaces/discussions/groups/libraries, etc. as well as mid-level views of business intelligence, Excel Services, Forms Services, and security.
Each chapter does a nice job of covering its topic with good introductory passages and a nice summary. Most chapters have a plethora of well-done, targeted screen shots backing up the content for that chapter. From time to time the particular author will call out pitfalls (nicely denoted with a trap graphic) and discuss issues surrounding that problem. I also like that the authors didn't try to push "Best Practice!" fluff throughout the book. (My biases come up here since 1) I hate the phrase "Best Practice" since it may be "Best" for you but completely "Suck" for me and 2) MOSS/WSS is too new to have solid, industry-wide guidance anyway.)
Overall, I've gotten some very good value out of the book and wouldn't hesitate to recommend it to others, aside from making sure it's understood that the book's not one for understanding the mid-level or more complex areas of WSS/MOSS.