Hail, Caesar! isn't easily accessible to those not fully immersed into the Coen canon for Even for Coen brothers, this one is an oddball. Is it just the random disjoint collection of episodes or is it a deep allegory that tells the story of the last temptation of Christ?
This film is the story of Eddie Maddix, a Hollywood fixer from the 50s who must keep the show going on against the ever increasing odds. His work is hard but it is important. The movies mean something. They are important. Much the way that opera or theatre was to the past generation, like to the Europeans. Maddix gets this. It is easy to miss that his sense of importance for the 'art of the picture' is the soul of this film.
As for the fun, just watch out for Ralph Fiennes trying to make Alden Ehrenreich say 'Would that it were so simple'.