"The Adobe Photoshop Lightroom2 book for Digital Photographers" by Scott Kelby, ISBN 13:978-0-321-55556-4 (yes, that's the first ISBN number I've ever seen with a colon in it).
"The Adobe Photoshop Lightroom 2 Book, The complete guide for photographers", by Martin Evening.ISBN-13:978-0-321-55561-8 (MMM, that's the second ISBN number with a colon).
Kelby is an easier read, Evening has a few things that aren't in Kelby (or I couldn't find). For a newb, I'd recommend
Kelby.
Beware that both have a Lightroom 1 version, which you don't want.
