Reddit mentions of Programming with POSIX Threads

I haven't read the book but after attending his talk not surprised to hear this at all ;-)

I still find David Butenhof's Programming with POSIX Threads the best introduction to thread-based concurrency even through there is zero C++ (modern or otherwise). But once you understand the fundamentals (like why you need to hold the mutex when calling wait() on condvar), then all the APIs (like that of C++11) become fairly transparent.

Sure, Programming with POSIX threads and Unix Network Programming, Volume 1.

Not as far as I know, but I've seen this book being recommended some times: http://www.amazon.com/Programming-POSIX-Threads-David-Butenhof/dp/0201633922/

I've never read it.

APUE is generally recommended (not specifically for multithreading though), and it has chapters on multithreading and multiprocess programming: http://www.amazon.com/Advanced-Programming-UNIX-Environment-Edition/dp/0321637739/

Obs.: People are talking about multithreading a lot, but there are other approaches. Multiprocess is another way to possibly take advantage of multiple cores on a CPU or multiple processors on a computer. Differences between the two approaches involve:

• what your OS defines as a thread and as a process (processes and threads are commonly OS supported concepts, but I've read about multithreading that doesn't require specific OS support for threads [green threads - check http://c2.com/cgi/wiki?GreenVsNativeThreads], but I've never heard multiprocess programming without the assumption of the existence of an OS that supports the idea of a process and of multi processes running "at the same time" [it seems possible to me to extend the notion of green threads and come up with something like green processes, but I've never seen that done out there]);
  
• what means through which threads can pass data around and what means through which processes can pass data around;
  
• the amount of resources it gets utilized to create and destroy a thread and a process;
  
• etc.
  
  Processes are generally heavier weight (they spend more resources) and are more isolated from each other, in comparison to threads.

If you're programming for POSIX environments, this book is an absolute reference. It's as old as pthreads, but still relevant, especially the explanation of various multi-threading paradigms, such as pipeline and worker group. Plus it's much better than OReilly's book on pthreads.
If you're developing for multiple platforms and want to stay 100% C++ /u/Meowiavelli 's recommendation is def. top notch.

I found this to be a useful starter.
https://www.amazon.com/dp/0201633922