The book is "LINUX Kernel Internals" by Michael Beck et al, translated
from the original German. Addison-Wesley, ISBN 0-201-87741-4.
Unfortunately, the preface to the second edition is dated August, 1994.
The book is about kernel version 1.2 (but hey, all the source is on the
accompanying CDROM 8-)
Chapters are: general/compiling kernel/intro to kernel/memory
management/IPC/file system/device drivers/network implementation/modules
and debugging. Appendices: System calls/kernel related commands/proc
fs/boot process/useful kernel functions.
This book is a fairly low level cookbook with lots of snippets of code.
It would be pretty tough reading for someone not already somewhat
familiar with UNIX internals in general; For that, use "The design and
Implementation of the 4.4BSD Operating System" (Addison-Wesley) or "The
Magic Garden", publisher unknown, about SVR4 internals.
I wish I knew in more detail how much has changed from 1.2 to 2.0/2.1.
If you want to write/modify/debug device drivers, the theory's the same,
but some kernel function calls have changed, I think. If you want to
know about SMP, non-intel specific architectures and other sexy stuff,
this book won't help.