As far as I can tell, the latest (December 2008) book dedicated to this one and only topic is
TCP/IP Architecture, Design and Implementation in Linux.
772 pages, enough to keep anyone busy for a little while.
Note that it doesn't cover UDP, deferred to a future book.
Caveat: Even though the book was released end dec 2008, the base kernel tree it describes is a 2.4.20 one. OTOH, I don't think the TCP/IP stack has changed that much since then. The author announces in his preface that 2.6 specifics will be covered in a future edition.