UnderstandingTheLinuxKernel is the title of a book by Daniel Bovet and Marco Cesati. 2001 edition is ISBN 0596000022
This is from OreillyAndAssociates and is the book at the left of the top shelf on the picture on that page.
There is a later edition also - see http://www.amazon.co.uk/books/dp/0596005652
See also LinuxKernel.