A very good way to start off this blog would be to talk about the history of z/VM. But, I don't have to say much because an article was recently published in z/Journal magazine about this very subject. The article is titled The Last 30 Years of VM by Neale Ferguson and it can be found at http://www.mainframezone.com/article/the-last-30-years-of-vm . This article doesn't discuss the very beginnings of the VM operating system, but does discuss VM in its "glory days" and its transition to the VM we have today. I think it is important to have some background on z/VM so that you can better understand why VM is designed the way that it is and why some functions and features are included that seem to have limited use these days.
For even more history of VM, including its early history, you should look at the papers written by Melinda Varian. These can be found on her page at http://www.leeandmelindavarian.com/Melinda/index.html. Scroll down for the "VM History" section to see the various papers in various formats, including e-book format!
Happy (history) reading!