Book evi Nemeth is undoubtedly good, and this is the basis, but not on system administration in General, and Linux. That is, if you plan to work with Windows Server, for example, then this book will help you a little.
I would advise A. M. Kenin - "the Tutorial system administrator"
. Just right for beginners, a little of everything. Once you understand the basics you can already move on, select a direction.