If you just want to learn it, need no credit, the best way is to teah youself. Internet gives you everything you need, more than what you could ever learn from any colleges. I became a Linux system admin by teaching myself with Internet and an old 586 machine. :-D BTW, in Linux world, all knowlege exists in "Howto"s, such as "kernel compile howto", "sendmail howto", "Xwindows howto" etc.
Do you need real books? literally, you don't. However, I got myself one at the beginning when I started off. Partly because at that time, Linux was not so hot yet, no good books around, and neither much howtos in internet. In some high level howtos, the authors tend to keep things short. You may need a entry level book handy all the time.
Good luck, and welcome to Linux world!