This book was quite charming. Sometimes it even was funny, in an almost absurd way. Overall I really enjoyed reading it; it was a lovely little compact book to read, the language was easily understood and the symbolism was very well-used.
I really liked how Sachar managed to intertwine two stories into one whole. The background-story of Kate Barlow matched the main-plot perfectly.
Some aspects of the book reminded me a little bit of "The Lord of the Flies". Y'know, bunch of boys in a closed society, the nicknames and the battles for power and dominance in between. It added a nice psychological dimension to the novel.
I may have liked this more, if I had read it a couple of years ago. I couldn't help but to be annoyed of the ending, which I really didn't think matched the plot at all. It kinda ruined the book for me.