While these listings are far from complete, they are the sources that I found the most useful and should certainly keep you busy for a long time.
If you are a new Linux user, the books by Powers or Siever are both good general references. If you want to know more about Linux system administration, my favorite is Nemeth. Frisch, a quicker read but less detailed book, is also a good place to begin. If you need more information on the Linux kernel, Bovet is a reasonable book to look at. For fine-tuning your system, Musumeci is a good resource. For a detailed overview of Unix security issues, you might look at Garfinkel. Limoncelli provides a general overview of system administration practices.
A robust network is a crucial part of any cluster. While general Linux books will take you a long way, at some point you’ll need more specialized information than a general administration book can provide. If you want a broad overview of networking, Tanenbaum is very readable. For Ethernet, Spurgeon is a great place to start. If you want more information on TCP/IP, Comer, Hall, and Stevens are all good starting points. For setting up a TCP/IP network, you should consider Hunt. For more information on firewalls, look at Cheswick or Sonnenreich.
Of course, setting up a system will require configuring a number of network services. Hunt provides a very good overview. If you need to delve deeper, there are a number of books dedicated to individual network services, particularly ...