First, a little context. I've been around the D community for a few years, keep a blog about items of interest to D users, maintain an open source D project and, in 2007, coauthored "Learn to Tango with D". Through all of that, the majority of my experience was with D1. I was hesitant, even reluctant, to use version 2 of the language because, in some ways, it is a bit paradigm shift from the first version. Andrei's book has dispelled any doubts I had about moving forward with D2.
D2 melds several different programming paradigms into one whole. One of the most radical differences from existing C-family languages is the concept of 'ranges', which are intended as an improvement over, and replacement for, the more familiar 'iterators' of other languages. Before the book, while ranges were being implemented in the alpha versions of the D2 compiler, some people had trouble wrapping their heads around ranges. Here, Andrei explains them in a way that makes them easy to grok and will have you using them in no time. And it's important that you do understand them as Phobos, D's standard library (which is intentionally not given much coverage in the book) has been reworked around the concept.
Aside from ranges and the more basic features of D which aren't so foreign, you'll also learn about D's interpretation of constness and immutability (D's const and immutable keywords are intended to improve upon the mess that is C++ const), and the D style of concurrent programming. D is poised to slot seamlessly in to the world of multi-core programming, with built-in features that simplify the process for those, like me, who can't think on that scale. Andrei's explanation of concurrency pitfalls and D's solutions should turn a light on for you if you're in the dark about it.
I've highlighted these particular aspects of the book because they are the areas about which I was most uncertain before reading it. But the entire book is well written, witty and easy to read. If you've never written a line of D in your life, you should have no trouble doing so after reading this book. I can't begin to speculate how much a beginning programmer might get out of it, but I would certainly recommend it to anyone who has at least a basic familiarity with another language from the C family. Andrei has that rare gift of taking potentially boring or complicated material and making it not only digestable, but fun.