Microsoft Press release free eBooks often and this is a nice one to have if you are responsible for maintaining Windows Server 2008 R2 (or just curious!).
Free eBook Article: http://blogs.msdn.com/b/microsoft_press/archive/2009/10/20/free-ebook-introducing-windows-server-2008-r2.aspx
Download eBook Direct (PDF): http://download.microsoft.com/download/5/C/0/5C0BD0AB-040D-4C56-A60B-661001012DDA/Windows_Server_2008_R2_e-book.pdf
Here is the book’s Content at a Glance:
Introduction xvii
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
Released in 2009