I am still in my first year of being more than a level 1 help desk tech. Google and Spiceworks get me through the break/fix issues pretty well, but I have started reading IT books on specific topics to get a more thorough understanding of the underlying technology and hopefully set my systems up for success throughout upgrades, maintenance etc. I'm also trying to learn about the basics of lots of things before settling on a specialization...
I'm hoping for some recommendations on books that help to round out a relatively green IT administrator's knowledge of how and why things work. Some examples of what I mean:
Servers for Hackers by Chris Fidao - When I'm not working as an IT admin, I develop WordPress sites for small businesses and nonprofits. This book was a huge help in acquiring the knowledge I needed to properly build and maintain Linux VMs running WordPress on nginx.
Networking for System Administrators by Michael W. Lucas - I'm reading through this right now because the details of networking have been an arcane mystery to me and I'm hoping to eventually be comfortable implementing pfSense. Since there's no concrete timetable on that, I figured I may as well learn the basics of networking itself instead of relying on tutorials or things like the pfSense Cookbook. Lucas does a good job explaining the basics of many very complex things, along with the tools to figure out which of those things is malfunctioning when there's a network problem.
So, are there any good books you remember reading that helped jumpstart your understanding on a particular IT topic? I'd love to find a good primer on virtualization in particular, but really anything that is well-written is awesome. Bonus if they're on Safari Books Online!