Haven't really had a 'best' novel. They've all been pretty average. Our school never chooses really cool books, like Animal Farm or Lord of the Flies or whatever. Just random coming of age stories about teenage issues...
The worst, as in the most boring, was Falling Leaves (the 'adult' version of Chinese Cinderella). Ack it was boring. The only set book I just couldn't finish.
The worst in terms of the most poorly written was City of the Beasts in year 10. My friends and I wrote a letter of complaint to the teacher about how awful her writing was. I still shudder to remember it...