This volume by Tim Haines of "Walking with..." fame is a handsome compilation of some (perhaps even all?) of the many ocreatures featured in those series. There is at least one late inclusion which did not feature in any of the series - and I seem to recollect that there may be a few other welcome interlopers representing more recent discoveries.
Each creature is allocated one, or, in some cases, two pages of background information and at least one "photo". This kind of space doesn't allow for any indepth review or discussion, but, that's not the purpose of this volume - its a quick overview of a host of more eye catching or significant species from our deep past.
The book would be ideal of as a momento of the Walking with Monsters, Dinosaurs and Beasts series - note that the "creatures" of Walking with Cavemen are not represented within this book - I guess because they wanted to retain the relatively more exotic feel associated with non-humanoid creatures.
It is pitched at least at an early secondary school level, but would be adequate for the interested laymen of any age greater than that. It assumes little prior knowledge, and is very accessible.
This book is suitable for those fascinated by ancient life (although not overly academic in their fascination) and who enjoyed the way in the which the "Walking with" series tried to depict a sample of that life. It is a colourful, vivid "family album" of many of the fascinating, improbable, and/or dramatic creatures which once walked this world.