I've now finally got into this book, and read it. Possibly because I had more time lately for reading.
I thought the premise was good and therefore did become interested, for example, as it dawned on me that this abduction had to do with religious craziness (rather then what I was anticipating it may be, sexual abuse).
But like others, there was quite a bit in the book that we were asked to accept and I would question - e.g. why didn't this intelligent girl go straight to the organisers of the book fair when she realised that she had lost her mother again? It's not like it was the first time it had happened to her and she should have known the ropes, I'm sure her mum would have spelled it out to her what to do should she ever find herself separated from her mother again. I also found it confusing, and the explanation a bit vague, that she then found herself in the U.S.A. I find it unbelievable that never once in all the time she was with the old man and Dorothy, that she didn't approach or talk to any other adults (particularly during the times when she was out with Dorothy) e.g. in a shop, and at the very least tell them her story. Her acceptance of the old man's explanations for her mother and her father not being available, would not have been sufficient to silence an intelligent young child (I would think), especially because the "granddad" was decidedly odd.
I found myself skimming the last few chapters.
I had given the book to my daughter to read and she enjoyed it a lot, so perhaps it is the "older and wiser" reader that would find much to question.