I stumbled on this book in the Menlo Park public library and really enjoyed it. I also wondered why I had never heard of PLATO. Very good read.
Friendly Orange Glow is unfortunately kind of overstuffed, meandering and political and focused excessively on bitzer, and misses so much of what PLATO/NovaNET were to so many people. Empire, avatar, oubliette, dnd, even moonwar, typomatic, Room B/C, night ops, pso, AIDS, TERM-test, cherry keyboard hoarding, stig bjorklund, the chem lab, the trs-80 running the satellite, lippold haken and the music room, bigfoot. I don't know if it's possible to write the PLATO story but FOG only skips across the surface.
Also interesting: a write-up of the second-ever TED conference (in 1990!) by Brian Dear!