Anthony Williams, author of the Boost threads library, is writing a book on C++ threading based on the upcoming thread support to be added to C++0x. I am definitely going to pick it up when it comes out on paper. Hopefully by the time the book comes out, the compiler developers will have a robust implementation of the threading libraries.
After years of messing with PThreads and Win32 threads, Boost threads have really made my life easier. Boost threads are simple and they sure help make your code a lot more readable. The only problem with Boost is that you have to install it separately and that can require a lot of researching and trial-and-error on older hardware and non-standard architectures. It will be nice to have threading built into the language standard like in Ada and Java.