My boys are obsessed with the Dinotrux books. So obsessed that they repeatedly check them out from the library and request us to read these books to them every night. I can understand the obsession if I think about it. I can see how the combination of dinosaurs and trucks can be very appealing to four year olds. I think Chris Hall is a genius to have created these characters. We haven’t watched the TV show yet because it seems a bit violent to show it to four year olds. And common sense media rates them as appropriate for 7+ years age group. But, we love to checkout these books again and again from our library. So far the books in this series that we checked out seem to be ok to read to four year olds.