From the link...
The free e-book includes content from three recent publications from Microsoft Press:
Introducing Microsoft LINQ by Paolo Pialorsi and Marco Russo (ISBN: 9780735623910)
This practical guide covers Language Integrated Query (LINQ) syntax fundamentals, LINQ to ADO.NET, and LINQ to XML. The e-book includes the entire contents of this printed book!
Introducing Microsoft ASP.NET AJAX by Dino Esposito (ISBN: 9780735624139)
Learn about the February 2007 release of ASP.NET AJAX Extensions 1.0, including an overview and the control toolkit.
Introducing Microsoft Silverlight 1.0 by Laurence Moroney (ISBN: 9780735625396)