Books on Unix Kernels
These books tackle the design and implementation of Unix kernels. The first five discuss a specific flavor of Unix, and the later two focus on issues common to all Unix variants.
Bach, Maurice . The Design of the Unix Operating System. Prentice Hall, 1986. A good discussion on the design of Unix System V Release 2.
M. McKusick, K. Bostic, M. Karels, and J. Quarterman . The Design and Implementation of the 4.4BSD Operating System. Addison-Wesley, 1996. A good discussion on the design of the 4.4BSD system by the system designers themselves.
M. McKusick and G. Neville-Neil . The Design and Implementation of the FreeBSD Operating System. Addison-Wesley, 2004. A good discussion on the design and implementation of FreeBSD 5.
J. Mauro and R. McDougall . Solaris Internals: Core Kernel Architecture. Prentice Hall, 2000. An interesting discussion on the core subsystems and algorithms in the Solaris kernel.
C. Cooper and C. Moore . HP-UX 11i Internals. Prentice Hall, 2004. A look at the internals of HP-UX and the PA-RISC architecture.
Vahalia, Uresh . Unix Internals: The New Frontiers. Prentice Hall, 1995. A superb book on very modern Unix features, such as thread management and kernel preemption.
Schimmel, Curt . UNIX Systems for Modern Architectures: Symmetric Multiprocessing and Caching for Kernel Programmers. Addison-Wesley, 1994. A superb book on the perils of supporting a modern Unix on a modern architecture. Highly recommended.