You don't need to be interested in cycling or the Tour de France to be fascinated by Alex Gibney's documentary. The director was originally recruited to make a film about Lance Armstrong's comeback in the 2009 Tour.
Along the way, it morphed from a conventional sports documentary to one about corruption and cheating. Gibney himself clearly felt betrayed by Armstrong and re-interviews him after his appearance on The Oprah Show, in which the cyclist finally admitted to taking banned substances to boost his cycling performance.
Perhaps surprisingly, what damns Armstrong the most here is not his use of EPO or his years of denying any wrong-doing, even when confronted by well-informed journalists like David Walsh and Paul Kimmage. It's his abuse of power. If he had treated those closest to him in a kinder, less bullying fashion, his self-pitying argument that everybody else was cheating too might have carried more weight. After all, the fellow cyclists who helped expose him – Floyd Landis and Frankie Andreu prominent among them – had themselves used EPO.
This isn't just a hatchet job. Gibney seems genuinely intrigued by what drives Armstrong and how his character changed after his comeback from his cancer operation. At times, for example, when he is struggling his way up Mont Ventoux during the 2009 Tour, Armstrong seemed genuinely heroic. (It is still uncertain whether he was racing "clean", although the overwhelming suspicion is that he wasn't.)
Gibney is also fascinated by the science behind Armstrong's feats. There is some excellent interview material here with Michele Ferrari, the genial and laidback doctor who helped Armstrong to "train" during his pomp. The doctor quickly identified Armstrong's incredible lung capacity – and geared the training (and the cheating) toward that.
Armstrong himself is too busy fighting his accusers, justifying himself and telling bare-faced lies to spare much time for introspective soul-searching. His tragedy is that his achievements, which once seemed so extraordinary, are now bound to be forgotten – and no one will ever know how good he was or could have been.