If you are a developer for the GNU/Linux system, this book will help you to:
a) Develop GNU/Linux software that works the way users expect it to.
b) Write more sophisticated programs with features such as multiprocessing, multi-threading, interprocess communication, and interaction with hardware devices.
c) Improve your programs by making them run faster, more reliably, and more securely.
d) Understand the preculiarities of a GNU/Linux system, including its limitations, special capabilities, and conventions.
I found the text very similar to Advanced Programming in the UNIX Environment which is a definitive guide for any UNIX programmer.