I would advise the following 3 books
Programming-NET-Components This is a good place to begin. It has about 100 pages on threading and is also the book I learned from.
The next book I would read is
CLR via C# - third edition This is also very good on the subject. I learned a lot from both this and the previous editions.
Finally I would read
Concurrent Programming on Windows; This is around 900 pages on threading and I am still digesting parts of it. This one is invaluable if you are really serious about threading.
I would advise reading the books in the order mentioned. They are all ones that should be on one's bookshelf.
Thanks
Ken