An interesting review
This book reminds me (vaguely) of a book I read when I was in the third grade: The Angry Planet, by John Keir Cross, which was full of unpleasant scenes with illustrations to match. It didn't have what I would call a "happy" ending. If a nine-year-old can enjoy Dana Dash then that's a good thing, with it's emphasis on STEM.
Dr. Cavor sure gets around the time stream!