Via Tim Sneath:
The British Library has published a new application allowing you to read some of the world's oldest books in an intereactive way.
Try the app directly here: http://ttpdownload.bl.uk/browserapp.xbap
More info here: http://www.turningthepages.com
I had a look at Alice's Adventures Underground:
You click or drag to turn the pages - definitely a Wow moment and should further fuel ISVs imagination into what can be done with WPF.