[.ca] The Amazonian Languages (ISBN 0521578930)

Great for the initiated:
The book is great if you already have a sound notion of linguistics. Even then, the languages described are so bizarre that some of the grammatical terms and phenomena will be hard to grasp from such a technical, dry work. But it's a great book anyway. Just to see a cohesive explanation on such little known languages and ever their reconstructed proto-language is quite a trip.