Caution: "Words, words, mere words, no matter from the heart." W. Shakespeare. Ground your learning in the heart, and in the fire of experience.
The New New Product Development Game by Takeuchi and Nonaka. Let me ask you to go to www.hbr.com and look it up. It's a Harvard Business Review article. It costs $6 (softcopy). If you need to see it before you buy it, contact me.
The Knowledge-Creating Company: How Japanese Companies Create the Dynamics of Innovation by Takeuchi and Nonaka. This is the stepping-stone to their discussion of "Ba".
The Concept of "Ba" by Nonaka and Konno. This article gives an introduction to this subject. "Ba" is the place or context where great teams perform.
Extreme Programming Explained: Embrace Change (2nd Edition) (The XP Series) by Kent Beck and Cynthia Andres. This may be the best written book on Agile. Certainly XP has a lot to add to the game.
Extreme Programming in Practice by Newkirk and Martin.
Working Effectively with Legacy Code by Michael Feathers. Great book if you have to work with legacy code. And who doesn't.
Ssh! We're Adding a Process by Mark Striebeck at Google. Story of how Ad Words (arguably the highest business value piece of software ever written) adopted Agile/Scrum.
Agile Retrospectives: Making Good Teams Great by Esther Derby and Diana Larsen. Retrospectives will normally be extremely valuable if you follow their advice. (If you just talk, and take no action, retrospectives could be a waste of time almost.)
Fearless Change: Patterns for Introducing New Ideas by Mary Lynn Manns and Linda Rising. One could argue that, since Agile is still new, we need these tools to influence others to adopt Agile. I think a better argument is that we need these tools to influence others because we are always learning what Agile really is. Extremely useful book, whether you are a team member, a Product Owner, a ScrumMaster or a manager.
Rolling out Agile in a Large Enterprise by Gabrielle Benefield. This is about Yahoo. Many good suggestions.
Software by Numbers: Low-Risk, High-Return Development by Mark Denne and Jane Cleland-Huang. This book explains what you should go to Minimum Marketable Feature sets to get incremental funding. Or...it pays to go Agile.
The Mythical Man-Month: Essays on Software Engineering, Anniversary Edition (2nd Edition) by Frederick P. Brooks. It includes the famous essay on No Silver Bullet.
User Stories Applied: For Agile Software Development (The Addison-Wesley Signature Series) by Mike Cohn. Key stuff.
Agile Estimating and Planning (Robert C. Martin Series) by Mike Cohn. Again, key stuff.
* * *There are many other great resources. This is a start. You may also want to look at earlier posts of this sort. Start here.