When cruising the MSDN-forums I found the following free e-book:

Introducing Windows Server 2008 R2, by Charlie Russel and Craig Zacker with the Windows Server Team at Microsoft.

Chapter 1    What’s New in Windows Server R2    1
Chapter 2    Installation and Configuration: Adding R2 to Your World    9
Chapter 3    Hyper-V: Scaling and Migrating Virtual Machines    25
Chapter 4    Remote Desktop Services and VDI: Centralizing Desktop and Application Management    47
Chapter 5    Active Directory: Improving and Automating Identity and Access    65
Chapter 6    The File Services Role    91
Chapter 7    IIS 7.5: Improving the Web Application Platform    109
Chapter 8    DirectAccess and Network Policy Server    129
Chapter 9    Other Features and Enhancements    147
Index    163

source (original MSDN post)

Download the e-book in XPS (28 MB) or PDF (11 MB).