From Red-Gate website you can download (for free) the ebook Performance Tuning with SQL Server Dynamic Management Views written by Louis Davidson (@drsql) and Tim Ford (@sqlagentman).
DMVs are objects that publish information about the health state of a SQL Server instance. They allow you to monitor the heart of the system to diagnose problems and measure performance. They represent a very good tool for DBAs and database Developer as well. Reading this book you will learn how to obtain information from the most frequently used DMVs in investigating query execution, index usage, session and transaction activity, disk I/O, and how SQL Server is using or abusing the operating system.
The editorial review is available here.
This book cannot miss in your digital library! And obviously you can buy the paperback on Amazon.