I know it's kind of lame question, but I need to learn how to improve my usage of this DBMS and I need a book (programmers do read books!). It's quite expensive and time-consuming to order form Amazon from my country so I'd like to take a best choice, I can.
So, what is the best PostgreSQL book for a developer?
PS For reference, I treat PostgreSQL as a DBMS not an application server, so I definitely do not need a whole book about its extensibility model.