Today's $10 book from APress at http://www.apress.com/9781430226536
is Pro LINQ Language Integrated Query in C# 2010
"Most books show the simplest examples of how to use a method, but they
so rarely show how to use the more complex prototypes. This book is
different. Demonstrating the overwhelming majority of LINQ operators and
prototypes, it is a veritable treasury of LINQ examples."
Adam Freeman is an excellent author who is good at providing practical examples of code.