I was looking for a very quick introduction to WordPress, and I was fortunate to chance upon this book.
The authors have done a stellar job in creating an extremely approachable guide to WordPress. This is one of those books with a very high Return On Investment for your time spent reading it. Plan on spending about a weekend, and make sure that you have a hosting service handy (ideally with cPanel and Fantastico) to try out the examples.
The book is targeted at WordPress 2.7 - and does a very decent job of describing all that you need to know about installing, configuring, and using WordPress. If you want to know how to manage your posts, pages, tags, categories, links, media, widgets, plugins, RSS feeds, and themes - this book covers it all.
The only downside that I might point out is that the book devotes a lot of space to the creation of custom themes - which could be considered a topic that is simply too complex for a visual style workbook. There's a lot of ground to cover here in addition to just WordPress ... PHP, HTML, CSS ... and this is where the book tends to lose some of its simplicity and purity of focus. (Note that if you're somewhat familiar with these technologies, you should have no problem following along.)
Notwithstanding that caveat, if you want to get a quick grasp of the lay of the land, this book works out just great. It was a highly enjoyable read for me - hence my 5-star rating.