My good buddy Mitch Tulloch just published a free eBook covering what’s new with Windows Server 2012 R2. The book has several pages covering IIS, and Mitch has done a terrific job covering it, as usual.
The book is available to download for free here, if you’d like to take a peek. IIS is covered in pages 79-84: http://blogs.msdn.com/b/microsoft_press/archive/2013/08/01/free-ebook-introducing-windows-server-2012-r2-preview-release.aspx
The book is specifically for MP, and a more extensive edition covering RTM is in the works.