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teach middle school social studies, and during any given unit, I keep books having to do with the topic we are studying on the chalk holder section of the chalkboard, so that they are visible to my students, and maybe capture their attention. If we have silent reading or quiet time while other students are finishing tests, etc., this series is the one that my students reach for. They go through these books over and over, and I see a lot of pointing to share the pictures and text. I almost didn't get the series, because I thought it might be too young, but I know that my 11-13 year olds choose these books over all others.
We own this book and also Prehistoric World: The Ice Age. Both of these books (and the rest of the series, I presume) have very good illustrations and handy fact boxes with enough basic information (and pronunciation guide!) that even a cursory reading is informative. A few of the animals covered--Indricotherium, Basilosaurus--may be familiar to you from the BBC series Walking With Prehistoric Beasts, but most were new to us. As far as age group goes, my 7-yr-old will look at these on his own and listen while I read the full text, but I would say they are on the more advanced end of his reading. My quibble with these books has been that they sometimes make statements about extinct animals' behavior without providing supporting evidence. It could be that the format of a children's book is not the most convenient place to do that, but since we are trying to promote critical thinking skills, it bothers me enough to knock off a star from an otherwise very enjoyable book.