Tips on books about network security

[Mat <matteo@spark.homeunix.org>]

Hi to everyone
I'm looking for a book or some other reference (web sites, mailing 
lists...) that could introduce me to system/network administration (like 
logs or account management, FTP/APACHE/SAMBA servers configuration...) 
and network security (authentication, kerberos, SSH, VPN, 
firewalling...), both in windows and Linux environment, some "must to 
have" in a system administrator's library...
I see a lot of books about these arguments, both free and not, so I 
would listen some words from who works in this field, and has to deal 
with day-to-day administrative issues.

Thanks
Mat