I think this is a great book, but not for the price ($19.95 MSRP and $13.57 on Amazon). It's only 64 pages, and as the other reviewers have said, it provides no new information. If your players have already read the Campaign Setting, or even some of the novels, then this book isn't worth reading, because they probably won't get any new insight, or information, from it.
Regardless of the price, it is an excellent book, because it is an easy way to introduce new players to Eberron without making them read the large Campaign Setting. It is the first Eberron book that seems to be designed for this purpose, and it does it very well. The artwork provides great visual identification that brings the game world to life, with short, easy-to-understand descriptions of practically everything that makes up the background of Eberron. From Dragonshards, to the different Eberron Races, to the role of magic in society, to the continents and the world -- it's covered in here. It fulfills this one role so perfectly that I gave it three stars, despite the price.
However, there are three major cons to this book:
1) It gives away certain secrets of the setting. It's not as bad as the Campaign Setting, but it removes a certain mystery, especially about the secret rulers of a far-away continent (and other things of this nature).
2) It's not a coffee table art book. There's too many words, and too much recycled art (from the other Eberron books), for it too be a good coffee table book. It also won't make sense to anyone who doesn't play in Eberron, as the descriptions really bring detail and interest to Eberron (and not the art itself). The pictures are pretty, but I wouldn't buy it for that.
3) The price is insane. $20 for 64 pages of recycled art? Wizards of the Coast already paid the artists for the original commission of the artwork, and now it seems they are seeking pure profit from this book. I can't recommend this book, despite how great it fulfills the one purpose perfectly, because of the price (even the lower Amazon price).
In short, it's a great book for introducing new players to Eberron, without making them read too much. The artwork is great, and wrapped in a neat little package. However, the price is exorbitant. If you don't mind spending the money on 64 pages, then buy it.