I'm happy to know you liked the book!
The May 2006 CTP version of LINQ had several changes in subsequent releases. Our book is based on Beta 1 bits (released in April 2007). Beta 2 differs from Beta 1 in terms of some new features added. While C# had very few changes, VB9 had more new features, mainly becuase they were not ready in Beta 1.
We are currently working on future releases of the book and in the next months we will update our blogs with updated information. Currently there is some documentation included in Beta 2 bits and in several blogs around. However, in general there are no major breaking changes between Beta 1 and Beta 2.
Marco