Professional Linux kernel architecture / Wolfgang Mauerer, Wiley, 2008
Here is a wonderful book full of well organized information for Linux kernel programmers. It is assumed that you know C well, and that you know a bit about operating systems. It will take you through the concepts, underlying structures, and implementation of the Linux kernel source in detail, current to 2.6.24 or .26. At 1200 pages, it is not a book to be trifled with.