I remember when it happened - on November 18, 1978 - but I had just turned 12 the month prior, so I was unfamiliar with the context and what were the triggering events. I had always assumed it to be something on the order of millennialism-gone-wrong; an anticipated End Of The World that failed to materialize, an attempt at self-induced Rapture.
I learned that not everyone "drank the kool-aid" voluntarily, for one thing. I also learned that what may have set things off was a visit from Congressman Leo Ryan and a crew of reporters - possibly the investigation itself, or the defection/rescue of a dozen or so People's Temple members who asked the delegation to help them leave. It's hard to say, and it's clear there were a number of additional contributing factors.
Most interesting to me were interviews with a number of survivors, including Jim Jones' son Stephan, and one of the reporters, Tim Reiterman. The show was a combination of re-enactment and the footage shot at the time during Ryan's visit.
Grim, but it was interesting to fill in some of the context. I also found a collection of articles written around the 20th anniversary. As we're coming up on the 30th next year, I imagine there's more to follow those and the History Channel's program.