Or maybe everything is in a cycle...

1. Develop XPS, awesome fixed format document and print stream format
2. Develop Silverlight, fantastic cross-platform, cross-browser plug-in for richer media and interactive applications
3. Write book introducing Silverlight 2
4. Implement some XPS support using Silverlight
5. Make first three chapters of book available for reading online as an XPS document hosted in a Silverlight viewer

Enjoy.