It's been a long time coming, but "Maven: The Definitive Guide" has finally hit the shelves. This was a collaborative effort with many authors and editors involved. I'll admit that in reviewing the book, I learned a thing or two, even though I've been a maven committer for 3 years and on the PMC for 1.5.
The book is comprised of two parts, the first is a learn by example step by step with sample projects, and the second is more in depth discussion of advanced topics like profiles, repository managers, eclipse ide integration, lifecycle, etc.
Since each chapter was written by experts on the topic and reviewed by the whole team, you won't find a better resource on Maven anytime soon, so grab your copy here