I don't think the books are suitable for a 7 year old to be honest, not with the stories of child beating and a man being murdered by his father. I read Shy Boy once and sold it on EBay, that was equine abuse in my view.
I give Monty credit for coming over and helping people to think about some things in horse training a bit differently (although if you had a western background it probably wasn't quite so earth-shattering). Having seen a lot of interesting trainers, I don't think he is anywhere near the best. I've seen Kelly Marks several times and was rather underwhelmed. However, I have been lucky enough to see some fantastic, slightly different, trainers so have some pretty subtle and skilled work to compare with.
I have read Horse Whispers and Lies, and I believe what the family say. For the simple reason that so many of the facts that they give can easily be verified (for example the comprehensive rodeo records show that Monty was not out and winning as he claims, and his attendance records at school). As for Join Up, it just didn't happen the way Monty says. He didn't go to the desert to capture mustangs for the rodeo. Why? Because none of the kids who were supposed to have gone could have driven. Also, people involved at the time have confirmed that nobody in their right mind would have trusted the important job of obtaining rodeo horses to a gang of teenage boys. If you read Monty's dad's book, which was published way before Monty was out doing his stuff, he described Join Up quite clearly as a technique he used. He called it Hook Up.
Er, I suppose I'm not a great fan then...
Oh, and the abuse from his father. It's very interesting that a horseman who wasn't well known when Monty wrote his first book was physically abused by his father... Buck Brannaman and his brother were so badly beaten and abused that they were taken into foster care. Buck Brannaman is of course the real inspiration for the book The Horse Whisperer, as confirmed by the author of the book.