Sanders was a friend of Glenn and JD at the time he was researching Manson. There are a couple of stories from that time. One has Glenn and JD turning up to look for Sanders at his hotel and causing panic because people thought they were Manson family, and the other has Glenn throwing milk bottles at Manson family members hanging around outside the place in Echo Park.
I don't remember where I got the 900 pages from, but in this interview, Sanders says it has 4 volumes.
http://www.georgepetros.com/writings...ds/sanders.pdf