I read Helter Skelter back in high school. Also watched a very freaky movie made from Manson Family home film and interviews with Family members. Looking back, it's stuff you'd rather wasn't put in your brain.
More recently, I read some articles about the Dennis Wilson's relationship with Manson that are pretty disturbing, including this
interview with Mike Love in People magazine.
So weird how California was such a mecca for cults in the 60s and 70s. I don't know if it's still available, but Netflix had a documentary about The Source Family and it's guru Father Yod. Crazy stuff. It seems young people with empty family lives + a culture celebrating rebellion against social norms + drugs + messianic sociopaths who want to sleep with loads of women = bad news.