Wow! I did not expect this book to be nearly as good as it is. What makes it so great? In a word -- completeness. Most books in this genre contain a bunch of entries about dinosaurs, and maybe a couple other oddballs thrown in. This book gives an almost unbelievable amount of detail about the most incredible forms of paleozoic, mesozoic, and cenozoic life. You will find hundreds of entries about relatively obscure creatures, from early tetrapods to obscure primitive plesiosaurs to esoteric early mammals. Nearly every important prehistoric group of tetrapods and their successors is addressed in loving detail. Interested in cynodonts? They're there. Rhyncosaurs? Of course. Placodonts? You bet. Gorgonopsids? Plenty. An absolutely wonderful comprehensive survey of land-dwelling vertebrates (along with those that later returned to the sea or took to the air).
Contrary to what some of the other reviews say, the book certainly does NOT contain anything like entries on every prehistoric creature, which would be totally absurd. But it does contain detailed entries on nearly every important vertebrate group on land and their descendants.
Finally, the illustrations are superb. If I had one fault to assign, it's that the book is a little too small. While very thick, a bit more height and width would allow more enjoyment to be taken from the delightful illustrations.
This book will NOT disappoint.