My 8 year old was very curious about this book. I could let her read some of it, but since she has not yet learned division and multiplication, the section on probability would be completely lost on her, which is a shame, since the probability theory so well explains unusual events. This is important, since so many superstitious people would attribute the unusual events to something superstitious; using probability to explain these events defuses their so-called "proofs".
My daughter will have to wait for a while, but she will definitely read it when she is older (and so will my other - younger - daughters). This is a must for every schoolkid 10 or older (actually, it's a must for just about anybody with any superstitious tendencies, including those who believe in horoscopes).