If you are really looking for a physical book on Linux, you should go to a physical, well-stocked, bookstore and browse the Linux books that are there. You will get a much better impression of what you want and what is out there.

If you might be looking for something to read online, check out the O'Reilly Safari site. It offers a huge selection of computer-related books for a cheap monthly fee.

Or, there are many sites that offer Linux documentation completely for free. One of my favorite sites is: http://linuxbasics.org/ (Oops, I see that site is shutting down. oh, well...)