A quick read that provides a clear and concise intro to Docker. This book does a good job of helping you wade through the buzzword soup that has been created by the Docker community. The debugging, deployment, and docker at scale sections are particularly valuable, as they are difficult to find in online documentation and blog posts.
As implied by the "Up and Running" subtitle, this is just an introduction, so don't expect too much depth or nitty gritty details. The biggest downside to the book is that the Docker community is moving so fast, that a larger and larger percentage of this book will become obsolete with each passing day. Of course, this gives the author a chance to publish new, updated editions periodically, which means you'll probably want a digital version of this book.