It is not easy to cram a description of 10,000 species into one book. What this book does brilliantly however, is introduce the reader into the world of birds through Orders and Families. Birds belonging to any such family are described in detail and their relation to other species in the same family or order are examined. Their evolution and closest cousins are also pointed out. The photographs are of the highest order, and there are plenty. Some species or topics, such as Kakapo conservation, are allocated extra sections.
The overall feeling is that this books is of great help in understanding the habitat, habits and ecology of groups of birds and their relationships without getting bogged down in species identification. I dont know how long it has taken to come up with this book but it is certainly worth buying.