The film chronicles 40 years in the life of a writer played by Philip Seymour Hoffman, who sets out to stage the ultimate play. He spends decades creating an enormous set with actors who mirror him and the many women in his life (Samantha Morton, Michelle Williams, Catherine Keener, Emily Watson and others).
Apparently, the viewers at Cannes weren't sure what to make of the film. The original version is over 4 hours long. That's the one I want to see.
Check out the cast - very impressive.
The Cannes has loads of info on the film as well.