This book is obviously meant for 10 year olds, who are always concerned about the size of anything. I bought this for my 9 year old grandson in order to perk his interest is science (but, of course, I read it first). He was duly taken by the pictures rather than the text. And therein lies the problem. The pictures of a number of prehistoric animals are exaggerated in size compared to their modern counterparts, either purposely, or out of naivety. A striking example is the book cover showing Liopleurodon about to devour an orca. The jaws of Liopleurodon are shown to be as long as the entire orca , maybe 25 feet long, while the text and description inside the book belies this size. Furthermore, neither the text or description comport with recent science, which says that Liopleurodon was likely a much smaller animal (still large but not gargantuan; see www.plesiosaur.com). There are apparently several other genera of plesiosaurs/pliosaurs which were considerably larger than Liopleurodon. But none are the size of the behemoth pictured on the cover.
Another example of out-sized illustration is the Tyrannosaurus attacking the cattle. Tyrannosaurus skulls are known to be about 4-5 feet long; this illustration shows them to be about twice that long.
I can understand the desire to emphasize the great size of some of these creatures in order to promote excitement, and sales of the book (and some of the descriptions of size are pure speculation). But this book also pretends to have a basis in factual fossil evidence. We all have fun speculating about things that could never be, but it's not appropriate to confuse silliness with science, especially in a book aimed at impressionable young minds.