There's a fun interview I ran across recently with Gary Lachman (a.k.a. Gary Valentine, early bass player for Blondie!) who knows a ton about this stuff. Though he's strongly biased in favour of Ouspensky against Gurdjieff. Pretty entertaining though, for anyone who likes esoterica about esoterica.
https://www.youtube.com/watch?v=lgurBMfwQw4