I am frequently asked for an Adobe Photoshop Lightroom 3 Book recommendation. If you are looking for such a book, check out Scott Kelby's The Adobe Photoshop Lightroom 3 Book for Digital Photographers.
Update: KelbyTraining.com has the The Adobe Photoshop Lightroom 3 Book for Digital Photographers on sale for $19.99 plus shipping. Unfortunately, shipping makes the final price higher than Amazon's price. The Kelby Training advantage is the inclusion of "The Adobe Photoshop Lightroom 3 Killer Presets CD with Matt Kloskowski ($39.99 value) absolutely FREE!" (thanks Edwardson)