This book is a companion piece to the television series of the same name. It is a work of fictional zoology which is a genre invented by Dougal Dixon. I have read all of Dixon's earlier work in this genre. The book looks ahead 5 million years, 100 million years and 200 million years. It covers four environments from each era and looks at about three creatures from each environment. In this is parallels the TV show exactly.
It is not clear to me how much input Dixon had on the creature designs in the TV show, but they certainly feel like his work. The book is quite light and is most suitable for chidren. It is not as good as the Television show in my opinion. I think that it makes more sense to just watch the TV show which is available on youtube. The big problem with the book is the art, which are stills from the TV show. The TV show's computer animation was quite primitive. In the book this is very noticeable. The book does not have the magic of the earlier books because of poor art. One plus from the show is that while the TV show was quite slow paced everything here is condensed so it is a quick and easy read.
As to the content, the inventiveness of the animals is very well done. My favorite is the Phantoms, but the whole thing is very inventive. While some of it is about convergent evolution, there are some utterly unique and very plausible creature concepts. In this it is the best of the alternative zoology books. I found it a bit of a downer that almost all vertebrates go extinct, but perhaps I am biased because I am also a vertebrate.
In addition, it is also very good at teaching why things evolve. A child reading it will learn about adaptive radiation, the roll of mass extinctions, and so on.
Its a wonderful flight of fancy and educational, but the presentation is lacking.