Adam Nathan (of .NET and COM and pinvoke fame) has been working on a WPF book - Windows Presentation Foundation Unleashed, which is now available for pre-order on Amazon. It's scheduled for release in mid-September, and will be around 570 pages long. This release, coupled with the Charles Petzold book "Applications = Code + Markup" which is supposed to be available a week earlier (and is also can be pre-ordered) will no doubt bring some great new perspectives on WPF development from these two excellent technical authors.
Recently Adam showed us an excerpt of some material from the book - the use of Vista's Aero Glass effects in a WPF application, which requires WPF Beta 2. I can't wait for the book to be released. I love the colour scheme of the cover too - don't shades of brown and orange look good together?