This is possibly my favourite documentary of all time and the perfect analogy/companion to the film it's about, Werner Herzog's 1982 masterpiece Fitzcarraldo.
This film hides nothing, it exposes filmmaking for what it is, a gruelling
and time consuming form of art and both can be proven since it took Herzog 5 years and a completely new lead actor to finally finish his momentous tale.
If you care even slightly for films, or you want to see someone else's burning passion for cinema then I highly recommend this.