The concise edition of Birds of the Western Palearctic is a set of 2 volumes in a nice sturdy presentation box:
Volume 1 - Non-Passerines
Volume 2 - Passerines
I'm very pleased with the books. Other books I already have are small paper-back pocket guide-type books of "Birds of Britain and Europe" that cost about 1/3 of the price of this 2 volume set. These are useful but the information in them is limited to the absolute basics of what the birds look like, sound like and where they can be found. Not enough to satisfy my curiosity. I wanted to know what they eat, where they nest, how many eggs they lay, what the survival rate of chicks is, how long they live, what their predators and diseases are and so on. The concise BWP answers some but not all of these questions and answers some questions I hadn't thought to ask. I'm very far from being an expert and these books are reference books so some of the terms are not in my active vocabulary. It's handy to have a dictionary within easy reach.
I was a bit disappointed about what seemed to me to be omissions, such as information on species longevity for example, which I thought wouldn't take up very much space. However, the books are packed with interesting data and they couldn't possibly fit everything into a concise edition. If they'd managed to get in all the information I wanted, it would have required more stars than Amazon allow.