LINQ is nothing but language integrated query and it can also be represented in lambda expressions as its also possible to be used via English phrases. If you want to learn LINQ, you can refer to the book LINQ in Action. Its a nice book and provides very deep knowledge and I think you must be aware about the power LINQ has got, you can do a lot for the collections be the source any... I also found LINQ very powerful.
As my experience LINQ in Action is good book for understanding the principles of LINQ, and LINQ-to-SQL in particular. C# in depth is good for understand how LINQ works at the language level and including query syntax, extension methods and expression trees. No matter if you are beginner.
I would recommend Essential LINQ by Charlie Calvert and Dinesh Kulkarni. It covers all the essentials as well as background information on important topics such as lambdas and extension methods are essential to a full understanding of how LINQ works. There is a short section on PLINQ, but this was an example of technology when the book was written.