[UNIX Programming] Books reading

Advanced Programming in the UNIX Environment, Second Edition I have the first edition of this book when I was in college. It's nice, precise, informative. The second edition also adds in the API difference between unix and Linux, which is great. I read this book several times, especially the process chapter. A must have book for unix programming
The Linux Programming Interface: A Linux and UNIX System Programming Handbook Well,well,well~~ Another classic unix/linux programming book. Love it, more detailed in API explanation and design info than "Advanced Programming in the UNIX Environment, Second Edition".
Pthreads Programming: A POSIX Standard for Better Multiprocessing Tedious. But over all a nice book..