Hello,

* The design of unix operating system (Bach)

* Modern operative systems (Tanenbaum)

* Operating Systems design and implementation(Tanenbaum)

I haven't done formal Computer Science studies, and I don't the time to read the three of them, but as I am working very close to the linux kernel, I am trying to sharp my skills a little.

I would further suggest:
  * kernel area: Linux Kernel Development [1]
  * OS area: Operating Systems Concepts [2]
  * systems area: The Linux Programming Interface [3]

Anyhow, while reading books it's ok in the beginning
to really have a progress in your learning progress
you should start looking at the code.


thanks,
Daniel.

[1] http://www.amazon.com/Linux-Kernel-Development-Robert-Love/dp/0672325128
[2] http://www.amazon.com/Operating-Concepts-Seventh-Abraham-Silberschatz/dp/0471694665
[3] http://nostarch.com/tlpi