I've used to have this list on a Google Spreadsheet, it took me quite a while to sort it (the first 3-5 books for each category are more essential than the others) and place the links, but here it is, more than sixty agile-related books! Agile Process

• User Stories Applied by Mike Cohn
• Agile Estimating and Planning by Mike Cohn.
• Agile Software Development by Alistair Cockburn
• Extreme Programming Explained by Kent Beck.
• Crystal Clear: A Human-Powered Methodology for Small Teams by Alistair Cockburn
• Accelerating Process Improvement Using Agile Techniques by Deb Jacobs
• Agile and Iterative Development: A Manager’s Guide by Craig Larman
• Agile Project Management with SCRUM by Ken Schwaber.
• Agile Project Management: Creating Innovative Products by Jim Highsmith
• Agile Retrospectives: Making Good Teams Great by Esther Derby and Diana Larsen.
• Agile Software Development in the Large: Diving Into the Deep by Jutta Eckstein
• Agile Software Development with Scrum by Ken Schwaber and Mike Beedle
• Agile Software Development, Principles, Patterns, and Practices by Robert C. Martin
• Behind Closed Doors by Johanna Rothman
• Crucial Conversations - Kerry Patterson, Joseph Grenny, Ron McMillan, Al Switzler
• Debugging the Development Process: Practical Strategies for Staying Focused, Hitting Ship Dates, and Building Solid Teams by Steve Maguire
• Joel on Software: And on Diverse and Occasionally Related Matters That Will Prove of Interest to Software Developers, Designers, and Managers, and to Those Who, Whether by Good Fortune or Ill Luck, Work with Them in Some Capacity by Joel Spolsky
• Manage It!: Your Guide to Modern, Pragmatic Project Management by Johanna Rothman
• Managing Agile Projects by Kevin, J. Aguanno
• Organizational Patterns of Agile Software Development by James O. Coplien, and Neil B. Harrison
• Practices of an Agile Developer: Working in the Real World by Venkat Subramaniam
• Project Retrospectives: A Handbook for Team Reviews by Norman L. Kerth
• Release It!: Design and Deploy Production-Ready Software by Michael Nygard
• Scaling Software Agility - Dean Leffingwell
• The Art of Agile Development by James Shore
• Smart, and Gets Things Done by Joel Spolsky
• Software Estimation: Demystifying the Black Art by Steve McConnell
• Waltzing with Bears: Managing Risk on Software Projects - Tom DeMarco and Timothy Lister

Additional Context

• The Goal - Eliyahu Goldratt
• The Mythical Man-Month: Essays on Software Engineering by Frederick P. Brooks
• The Five Dysfunctions of a Team: A Leadership Fable by Patrick M. Lencioni
• The Fifth Discipline by Peter M. Senge
• Fearless Change: Patterns for Introducing New Ideas - Mary Lynn Manns and Linda Rising
• Slack by Tom De Marco.
• Peopleware: Productive Projects and Teams by Tom DeMarco
• Collaboration Explained by Jean Tabaka

Agile Development

• The Pragmatic Programmer: From Journeyman to Master by Andrew Hunt and David Thomas
• Pair Programming Illuminated by Laurie Williams.
• Test Driven Development: By Example by Kent Beck.
• Domain-Driven Design: Tackling Complexity in the Heart of Software by Eric Evans
• Code Complete: A Practical Handbook of Software Construction by Steve McConnell
• Continuous Integration: Improving Software Quality and Reducing Risk by Paul Duvall, Steve Matyas, and Andrew Glover
• Design Patterns by Gamma et al
• How to Break Software by James Whittaker
• Pragmatic Project Automation: How to Build, Deploy, and Monitor Java Apps by Mike Clark
• Refactoring Databases: Evolutionary Database Design by Scott W. Ambler, and Pramodkumar J. Sadalage
• Refactoring by Martin Fowler
• Refactoring to Patterns by Joshua Kerievsky
• Test Driven: Practical TDD and Acceptance TDD for Java Developers by Lasse Koskela
• xUnit Test Patterns: Refactoring Test Code by Gerard Meszaros
• Working Effectively with Legacy Code by Michael Feathers
• The Practice of Programming by Kernighan and Pike

Lean

• Lean Thinking by James P. Womack and Daniel T. Jones
• The Machine That Changed the World by Womack, Jones and Roos
• Lean Software Development by Mary Poppendieck and Tom Poppendieck
• Implementing Lean Software Development: From Concept to Cash by Mary Poppendieck and Tom Poppendieck
• The Toyota Way by Jeffrey Liker
• Toyota Culture: The Heart and Soul of the Toyota Way by Jeffrey Liker
• Toyota Production System: Beyond Large-Scale Production by Taiichi Ohno
• Gemba Kaizen by Masaaki Imai
• Kaizen and the Art of Creative Thinking by Shigeo Shingo
• Lean Software Strategies by Peter Middleton & James Sutton
• Lean Solutions by James P. Womack and Daniel T. Jones
• Scaling Lean & Agile Development - Bas Vodde and Craig Larman