For a technical, in-depth overview of IncludeOS and how it was made I find the main authors presentation at Cppcon 2017 is a pretty good introduction:
https://www.youtube.com/watch?v=h7D88U-5pKc (one hour, quite entertaining).
There is also the original paper which was presented at the 2015 IEEE 7th International Conference on Cloud Computing Technology and Science (CloudCom).