Already accumulated an impressive stack of materials on Windows Server 2012 and Windows Server 2012 R2 . I decided for convenience to bring all the links in one post. I hope it will be useful.

General issues

What's new in Windows Server 2012 R2?
GUI, not GUI - or how to enable and disable the graphical interface in Windows Server 2012

Hyper-v

New features of Hyper-V 2012 R2
Private VLAN support in Windows Server 2012
Hyper-V Extensible Switch in Windows Server 2012
Shared VHDX in Windows Server 2012 R2
The second generation of virtual machines in Windows Server 2012 R2
Configuring Hyper-V Replica in Windows Server 2012
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SMB 3.0

SMB Multichannel in Windows Server 2012
SMB Transparent Failover in Windows Server 2012
SMB Scale-Out in Windows Server 2012

Storage

Storage and High Availability in Windows Server 2012 R2
Overview and configuration of deduplication tools in Windows Server 2012
Creating Clustered Storage Spaces in Windows Server 2012

Network technologies

NIC Teaming on Windows Server 2012
BranchCache in Windows Server 2012 and Windows 8
Update Remote Desktop Services features in Windows Server 2012

Hyper-V Network Virtualization

Network Virtualization in Hyper-V. Concept
Network Virtualization in Hyper-V. Customization
Network Virtualization in Hyper-V. What's new in Windows Server 2012 R2?

Dynamic Access Control

Dynamic Access Control: Reshaping Resource Management
Dynamic access control: how to work with assertions
Dynamic access control: what resources are
Dynamic Access Control: Resource Property Lists and File Classification
Dynamic access control: working with centralized rules and access policies