Not on Online Education - but I have done a fair amount of work in the industry and this is one of the more referenced books: https://www.amazon.com/Smartest-Kids-World-They-That/dp/1451...
This is a good blog on the state of online education: http://mfeldstein.com/
And a really good article: https://www.fastcompany.com/3062958/how-google-is-schooling-...
To answer why top Universities bet on MOOCs: this is partly an attempt to get around Education's Iron Triangle (ref: http://www.adaptivelearningworld.com/?p=110)