I think you shouldn't pay money for any of those books (if you had in mind to pay for them, that is). Although I didn't read them, I bet the information you'll find in this books is widely available on the net.
If I were you, I'd try to focus a bit on texts about the understanding, the security and the hacking of a linux system, since the majority of the servers out there run on some kind of linux version.
Also reading the info from this post
will also provide a good starting point (if you haven't read it allready).