I didn't really like the book at all for the first 3 sections - I felt like it, ironically, didn't give ENOUGH detail.
But then I got to Chapter 12, titled "LINQ beyond collections" and, honestly, was stunned. I'd guess that most of the people in my circle believe that LINQ is a shiny object rather than a powerful functional tool which enables a wide variety of use cases.
So, with that said, bravo, Mr. Skeet. In terms of recommendations, I'd be more likely to refer people to chapters of the book rather than saying, "this is a book that you should purchase", especially in light of the many references to other web sites for clarifying detail, but in the right hands (for example, for people who savor academic learning!), this is a winner.