I've been using Linux mainly at the application level for a
few years now, and decided to go down to the kernel level. This book gave me a good introduction into the kernel internals. But I did find this book a bit heavy on code description, that I could of dug up myself. Telling me, which functions are called in a long descriptive list isn't really required if can view the source code yourself.
I also like lots of pictures to explain complex components such as memory management, the filesystem, etc. The pictures weren't bad, but could of been better. Why not describe a component based on pictures in each Chapter.
Overall a good start to learning the Linux kernel.