I probably wouldn't to be able to give a definitive answer on why I don't particularly like Max. His appearance (or rather lack of) seems to more or less reflect himself as a whole: non-distinguishable if not for the eyes. The eyes that everyone makes a note of and then completely fail to notice in his other disguises.
A lot of the things in this book, including the interaction of the characters feels heavily contrived, and it's not helped by the detached prose that accompanies it. It gives it a kind of wispy feel that doesn't really fit with a plot about kidnapped parents, though I suppose that fits, considering that I personally found it difficult to be upset about the kidnapped parents when it seemed dubious to me and all the other characters that they had just swanned off without a care in the world. Hardly a ringing endorsement of their personality if everyone is put into doubt as to whether they would actually completely abandon their child.
I wished Pia had been introduced earlier because she was what really made it possible to sit through the second half of the book, where the glaring plot points just burned through me, and though Max does figure it out, this presumed subtlety made it rather frustrating for me. I think probably it would be less noticeable for the intended audience, but I feel that's something of an unfair thing to say, that a book shouldn't be expected to be as suspenseful due to its intended audience. Possibly the most frustrating thing about Max is his inability to accept help, not exactly an uncommon fault in people, but Max singularly seems to resent
help, not feel awkward receiving it, or unworthy of accepting it, but actually resenting it
and I think that got to me more than anything. However, I did end the book feeling like I had to know if we watch him improve as he grew older, so it did that.
Overall, the plot was intriguing. There are a few subplots that follow from one to another and I did like Grammie, Ari, and Pia, though Ari's personality was a bit more informed than it was presented. I would recommend this book to twelve year olds, it's just that over that age I think Max's age may begin to grind.