I just saw that John Kelbley and Mike Sterling have an updated version of their Hyper-V book hitting the shelves next month.  Windows Server 2008 R2 Hyper-V: Insiders Guide to Microsoft’s Hypervisor is available for pre-order now.  I have a copy of the previous Windows Server 2008 edition which gave a great insiders view into Hyper-V; both authors work for Microsoft as a part of the Hyper-V product group.  You can bet that the new book will be an informative read.