The book covers the subject well enough but I find it badly written. I am only at chapter 3 describing LINQ to objects. There have been quite a few annoying paragraphs so far but finally I got to one that made me come online and write this review. They are trying to explain the group joins and here is how they do it: "You can think about this operator (GroupJoin) like a SELECT ... FOR XML AUTO query in Transact-SQL. In fact it returns results hierarchically grouped like a set of XML nodes nested within their parent nodes, similar to the default result of a FOR XML AUTO query". I am sure there are many developers with a lot of XML query experience but I am not one of them, just a basic understanding of XML. As far as I am concerned, it's rubbish. At least they cover the subject, but badly.