To begin with, let's have a look at the main characters, starting with Eddie Mannix. It turns out that there was an actual fixer in Hollywood named Eddie Mannix. He worked for MGM and was responsible for cleaning up scandals for many of their stars so that they could maintain their squeaky-clean images. The Coens actually made Mannix a lot nicer than the real one; movie Mannix is a family man and devout Catholic. The real Mannix led a dissolute life and was suspected of having something to do with his first wife's death in a car accident.
These are a lot of the character types and situations which the Coens lifted from real life: no doubt there are more which I've forgotten or overlooked. In any case, In my final post on the film, I'll discuss why I enjoyed it so much.