The administrative tools differ on each major distribution, so we can provide good recommendations if you can explain the reason that you want to learn about Linux based systems or the distro that you wish to learn.

As for the basics, the kernel and basic background functions are the same for all distros, however to get enough information to be of value it would best to learn the basics of your chosen distro and get books onthe applications that fulfill the tasks that you wish to accomplish. Such as getting a book on Apache HTTP if you want to know about web servers, Squid if you want to setup proxys, etc... The brief explanation for this is that the tools and possibilities on Linux based systems are very in depth, so if you have immediate need then it is best to focus on the immediate goals.

This site has some good resources for learning the basic functions of a Linux OS, basic and Advanced. If you want to get certified, this is a great place to start.

LPI