A new book on WHS was published last month (September 13): Microsoft Windows Home Server Unleashed by Paul McFedries. Very thick, 912 pages.
What's interesting is that the author not merely pointed out which buttons to press -- that's something we tried to make evident without books -- but also described some non-trivial hacks including meddling with registry settings, home network diagnostics and installing Sharepoint Server on WHS. While I cannot officially endorse using undocumented features, it's an impressive investigative work.
And that's not all. The next book Windows Home Server For Dummies by Woody Leonhard comes out in November. This one is more compact, 382 pages. I still did not see it, but according to the Amazon's description, it's purely a user-level book without much complexities or technicalities. Which, considering the target audience for Windows Home Server, is likely to be the right level useful for real users of WHS.
Pardon for using images with ad links -- that was the only way to show the covers legitimately, without violating the copyrigts. Anyway, feels great that they are coming. It's a really pleasant sensation when people start to write books about something that you created :-) Thanks to the authors for their great work!