Threads Primer: A Guide to Multithreaded Programming
I would describe the books as concise, precise and extremely readable. The authors use fluid language and use the right technical terms in the right places. One of the best Computer Science books I have ever read. Definitely a good reference(though the book is not a comprehensive Operating Systems book) for a beginner who is looking to gain conceptual knowledge about Operating Systems in general and Multithreading in particular.