Maurice J. Bach's classic "The Design of the UNIX Operating System" is based on AT&T's System V (Release 2 and 3). To avoid legal issues he had to use pseudo code as well as algorithmic description for explaining a lot of the operating system's underpinnings.

While some reader's might have preferred a glance at the related portions of the UNIX source code, others will be glad that MJB used this layer of abstraction to make the subject matter at hand easier accessible and understandable.

Even though UNIX has progressed from this snapshot in time, the solid understanding of the internals and underlying concepts that can be gained from this easy to read text will prove helpfull for a better understanding of other UNIX derivatives, too.

While this title is a "must read" for any advanced system administrator, as well as for system programmers, it's generally overkill for the average UNIX end user.