My six-year-old (or 6.5, to be as precise as he likes to be), Dad, and Mom all LOVED this book! It was exciting for him to read about these things. He thought it was all very cool. But also - he's always been a bit scared of rides, in general, and it seemed to make him feel better/braver when he was able to get some understanding of why amusement park rides are scientifically 'safe'. As far as the level of the scientific explanations, he followed most of the explanations just fine, but Dad and Mom were around while he was reading out loud to enhance the explanations and make them easier to understand, as needed. We invented to real-life 'tests' for what was being explained, so it became pretty interactive. I bought several books from this series and we can't wait to read all of them!