The preview bits for System Center 2012 R2 were released as part of "Blue" server announcements at TechEd 2013 Europe, and we have several articles written to help with the coverage. Here's a couple examples key to understanding what is available:

Mostly just a skeleton with "coming soon" tags and a download link, Microsoft has put together their own resource page to help customers get to know the upcoming System Center 2012 R2 release. The resource page currently offers information on system requirements, provides evaluation and installation guides, and also offers the ISO for download. What's missing, but "coming soon," is the System Center 2012 R2 virtual labs and online training.

Microsoft is providing this new resource partly to help pacify those customers upset by Microsoft's recent announcement that they are retiring the TechNet Subscription service. Ironically, the resource page also boasts an advertisement for TechNet, suggesting that, with TechNet, subscribers can evaluate software longer and enjoy access to expert support. That's like pouring salt in a wound, right there.

Here's a screenshot for your memory book:

The new resource page is located here: Microsoft System Center 2012 R2 Preview Evaluation Resources