Must-read Books for DBA
I started with an example of good must read book.

An Introduction to Database Systems by C.J. Date.

This is one of the most influential book to development of all concepts and technological available today. The book follows an academic style and has lots of real cases.

The primary target is not for DBAs but Database systems developers, but a real good DBA knows how your database works and how to handle with its limitations and hidden capabilities.