For many fanatical Mass Effect 3 fans, talking about the game's controversial ending for 84 minutes probably doesn't seem like a big deal. When those 84 minutes are packaged and edited as The Indoctrination Theory, a feature-length documentary, the discussion seems much more sensational.
As the name implies, The Indoctrination Theory is a detailed chronicle of the rise and proliferation of the "Indoctrination Theory" phenomenon, with believers talking about the many variations on the increasingly popular idea that the last 20 minutes of Mass Effect 3 actually took place in Shepard's head as the Reapers attempt to indoctrinate him.
One thing everyone shown in the film has in common: Even with their personal rationales in place, none of them liked the game's ending: In their minds, the series never really ended.
If you've heard about the indoctrination theory before and want to know what all the commotion is about, the film is an incredibly detailed primer on the topic. More importantly, it's a token of recognition that the controversy over Mass Effect 3's ending is a cultural phenomenon unto itself.