Apress' Pro Ubuntu Server Administration is described by its author, Sander van Vugt, as the best book he's ever written; he should know -- it's his fourtysecond book.
The table of contents is mouth-watering: server installation, system imaging, performance monitoring and optimization, file system management, network monitoring, SAN, configuring OpenLDAP, integrating Samba, adding a mail server, server security, setting up an OpenVPN server, Kerberos and NTP, topped by troubleshooting. The list contains almost all an administrator wants to have to set up an advanced server in an enterprise environment.
The chapter on SAN contains goodies such as DRBD and iSCSI and, as in most chapters, you learn to set them up more in a howto fashion, with a bit of background information. IMO there isn't enough background coverage to get the reader up to snuff -- if something goes wrong, I'm left in the rain. For example, when covering the Distributed Replicated Block Device (DRBD), Sander shows me how to set it up, but he doesn't really show me what to do if things go wrong -- and believe me, they do sometimes go wrong! Similarly with the section on iSCSI: the book tells me that I can set up authorization for iSCSI, but doesn't go into the details on how to do so.
In the OpenLDAP chapter, Sander says you set up replication of directories with slurpd, but doesn't show me how to do so, which is fine, because slurpd has been obsoleted from OpenLDAP! The chapter on Kerberos unfortunately doesn't explain how to store your Kerberos information in OpenLDAP -- a shame. The promising SAN and hearbeat sections show me how to set up a secure file system environment, but getting my OpenLDAP directory and authorization/authentication systems set up securely isn't covered.
Pro Ubuntu Server Administration is good for intermediate system administrators who want to get an enterprise-type server running fast. But don't forget, there is more to following quick instructions -- you want to be able to maintain the server. Hopefully a second edition will address those points.