I have quite a few books, mostly acculated from charity shops and second hand bookshops... but one of the very few I bought new was the first volume of the Baesch Aquarium Atlas series. In my opinion, the Baensch book is much better than the Axelrod mini atlas, which is otherwise similar. What I like about Baensch is the level of detail and the way it is quite obviously based on experience rather than re-hashing stuff from other books. There are lots of comments from the author about personal experience of a certain fish, or his opinion of the animal in captivity, and so on.
Cheers,
Neale