Carlyle’s axiom that the true university of these days is a good collection of books has remained valid as far as I am concerned, and even today I am convinced that one can become an excellent philosopher, historian, philologist, lawyer or what you will, without having attended a university or even a Gymnasium.
Stefan Zweig (The World of Yesterday)
Free Software, Free Societey: Selected Essays from Richard M. Stallman
Recommended reading for every GNU-Linux-enthusiast. The book is available as a free pdf document from gnu.org.
How Linux Works – Brian Ward (No Starch Press, ISBN-13: 978-1593275679)
A good beginners book on what is under the hood of Linux, the shell, file systems, networking it is all there. Good if you have no book on Linux yet.
The Design of the UNIX Operating System – Maurice J. Bach (Prentice Hall, ISBN-13: 978-0132017992)
Released in 1986 this is a classic and explains the nature of UNIX, topics like “System boot and the init process” and “processes” apply to a broad exent to modern Linux.
THE LINUX PROGRAMMING INTERFACE – Michael Kerrisk (No Starch Press, ISBN-13: 978-1593272203)
This book belongs to the heavy artillery of the Linux system books. A lot of information about processes, programm execution, threads … basically all you ever wanted to know about Linux.