There are a lot of Agile-related books out there, but here are a few of my favourites:

• Agile Retrospectives: Making Good Teams Great
  by Esther Derby, Diana Larsen, Ken Schwaber

• Coaching Agile Teams
  by Lyssa Adkins

• Succeeding with Agile Software Development
  by Mike Cohn

• Kanban and Scrum – Making the Most of Both [free via infoQ]
  by Henrik Kniberg, Mattias Skarin

• How to Change the World: Change Management 3.0
  by Jurgen Appelo

For a more extensive list of books, check out my Agile bookshelf on GoodReads and my Agile wishlist on Amazon.ca.

If there’s something missing from my list which you would recommend, please leave a comment or use the contact form.