Recommend a good intermediate level read on Office IT environments.

I manage a mid size law office (30-40 people) and while I have an IT provider who handles my day to day troubleshooting on our servers and network, over time I have taught myself to handle many of the basic to intermediate level issues. I don't ever expect to be IT free but if there are any reads that would be beneficial please pass them along. I know this is pretty broad subject so feel free to pass on any suggestions.

For those that would want to know what type of environment we operate in, we operate with a hyper-v, 2 physical host with 4-6 virtual servers. Email is Office 365 and the firm is running Office 2013 on Windows 7 desktops.