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.