Well, I've got a bit behind in my reviews; but here we go.
City of the Beasts is actually a teenage/tween book, obviously misfiled by the library staff. I have read one other of Allende's books. I enjoyed it, but it had strong overtones of "Amercia the saviour of the universe", which I don't enjoy.
This book, City of the Beasts, is set mainly in South Amercia. A 15 yr boy is sent to live with his grandmother, while his mother undergoes chemotherapy. Nana (Kate) is a bit of an odd ball and bundles him off to the Amazon with her. She's a reporter/writer and has been assigned the job of tracking down the South Amercian "Big Foot".
The book has some really heavy environmental protection messages; some really heavy human rights protection messages; and some sterotypical baddies. The messages are probably long overdue. South Amercian environment and native cultures could probably do with some heavy handed protection.
It was an interesting read, but it felt like it didn't really know which genre to aim for. It's not quite fantasy, not quite adventure, not quite eco-story.
I'd give it a about a 3.