Recommended reads
7 Habits of Highly Effective People

A classic in personal improvement books, and a lot of good things for project managers. Particularly I found the part on dealing with people the most inspiring for project managers ("Fast is Slow, Slow is Fast"). I really do recommend this book on a personal level as well.
Agile and Iterative Development

Essential book about agile and iterative methodologies. The book reviews the leading methodologies: Scrum, XP, Unified Process and EVO. But first in gives an historical perspective in the creation of those software development methods as an alternative to the failing waterfall model. Very interesting read just for that matter.
Finally there are some practice tips for project management and requirements management.
The only frustration I have is that the book only focuses on software development and does not address the application of Agile in a wider perspective.
Critical Chain

From the author of "The Goal", "Critical Chain" goes into more details on what is critical chain planning. The book is written like a novel so it's kind of entertaining to read (meaning less boring than the PMBOK!). The book first explain the theory of constraints, the identification of the bottleneck in project resources and how to build "buffers". A really good read that leaves you with the desire to go deeper into practical work on critical chain planning.
The definitive guide to project management

The Definitive Guide to Project Management: The Fast Track to Getting the Job Done on Time and on Budget (Financial Times Series).
I read this book as I was preparing for the PMP exam. This is a good study book because it follows the structure of the PMBOK (3rd edition), but in a concise and more readable way that the PMBOK. Before engaging with a knowledge area of the PMBOK it is a good idea to read the same knowledge area from this book to get the essential message.
If you are already a PMP then I don't think this book is really bringing significant value.