1. A List of books By Mark Levison for New Scrum Masters who want to improve their trade craft. Twitter: @mlevison
2. Scrum Beyond the Basics
   1. Succeeding with Agile
   2. Agile Estimation and Planning
   3. Agile Software Development
   4. Agile Retrospectives
   5. Collaboration Explained: Facilitation Skills
3. Beyond the Team Level
   1. Manage Your Project Portfolio
   2. Scaling Lean & Agile Development
   3. Scaling Software Agility
4. Not Agile Per Say but very useful
   1. The Wisdom of Teams
   2. A Sense of Urgency
      1. Scrum/Agile Transitions happen for a reason, this is your Sense of Urgency and a Tool to focus minds. Without urgency there is no reason to transtion.
   3. Buy-In: Saving Your Good Idea from Getting Shot Down
   4. Your Brain at Work
   5. Thinking in Systems a Primer
5. Coaching/Teaching Agile
   1. Coaching Agile Teams: For ScrumMasters, Agile Coaches, ...
   2. Agile In a Flash
   3. Agile Coaching
6. Explaining Agile to Management
   1. The Leader's Guide to Radical Management
      1. Your VP and CxO don't care about Scrum. Steve Denning explains what is effectively Agile in a language your manager can appreciate.
7. Lean and Kanban
   1. Lean Thinking
   2. Kanban: Successful Evolutionary Change
   3. The Principles of Product Development Flow
   4. Kanban and Scrum Making the most of both
      1. Free
   5. Leading Lean Software Development
      1. Really any of the Poppendieck's book are worth reading
8. Testing - Which includes clarifying requirements
   1. Agile Testing: A Practical Guide for Testers and Agile Teams
   2. Specification By Example
   3. Lean-Agile Acceptance Test-Driven Development
      1. See This interview with Ken that outlines ATDD
9. Technical Books - there many more than the few I list here
   1. Clean Code
   2. Growing Object Oriented Software Guided By Tests
   3. Working Effectively with Legacy Code
   4. Continuous Delivery