Considering the topic, SQL Server 2008 Query Performance Tuning Distilled is short, sweet, and to the point. It tackles what is a complex topic and does it in a manner that even someone who is relatively new to SQL Server and performance tuning and pick up in a short time.
Most people let SQL Server handle the heavy lifting until problems arise and then don't really understand what is going on in the black box. SQL Server 2008 Query Performance Tuning Distilled helps you to understand just what is going on inside. It is that what makes this book such an invaluable investment. It brings you up to speed slowly at first and then adds on layer by layer all the way to advanced topics.
If you need to get up to speed with performance tuning on your SQL Server then you need to look no further than SQL Server 2008 Query Performance Tuning Distilled. I very highly recommend this book.