Martin Evening is one of the most respected writers for digital photography. I haven't read any of his books before, though have one of Scott Kelby's books.
I must say I prefer Martin's style to Scott's. Scott tells you in easy steps how to accomplish different tasks, though doesn't explain the whys. Martin also explains how to complete various tasks, though explains why you carry out the various steps, to enable you to understand how to change the steps to achieve other results.
This book is the reference that should come with Lighroom. I've been using Lightroom since the PC beta came out, and over time have learnt to use much of the tools, but this book fills in a lot of the gaps, and extends my knowledge and speed using the application.
If you do not process many images, and got Lightroom to catalogue your images, then you will learn from the book, but you will gain so much more if you process large numbers of images (especially RAW) and want to refine your workflow, learn how to make the most of the cataloguing offered by Lightroom.
In short, if you want to spend less time behind your monitor, and more time behind the camera, buy this book. It's in depth, and yet beautifully clear, and laid out.