A new Master Data Services book is now available on amazon.com.
Microsoft SQL Server 2008 R2 Master Data Services; by Tyler Graham and Suzanne Selhorn; ISBN 007175623X
This book was written by two members of the Microsoft MDS team and is a resource and reference for using the SQL Server 2008 R2 version of Master Data Services. A Kindle version is also available.
An updated version of the book will soon be available for SQL Server 2012:
Microsoft SQL Server 2012 Master Data Services 2/E; by Tyler Graham and Suzanne Selhorn; ISBN 0071797858