This is one of the more successful attempts at making a film about a character going through a spiritual crisis. Most films that delve into this subject make a fatal error where the main character(s), in response to his/her crisis, decides to make stupid and irresponsible decisions (ala The Arrangement, American Beauty, Revolutionary Road) that seems to just complicate the situation. This can insult the intelligence of a competent, responsible audience. Arguably, there is some truth to people deliberately rebelling in some vain attempt at escaping responsibility, but when this occurs at the expense of other people--it is hard to watch for entertainment or educational purposes (especially multiple films about similarly stupid people).
HOWEVER, A Serious Man is a film where a character maintains some sort of smart, God-given optimism in spite of an ordeal. He is not blind to his issues, but simultaneously does not allow them to overwhelm him. He dreams about rebelling, but the same dreams offer humorously morbid moral lessons and conclusions. Writer-directors Joel and Ethan Coen cleverly surround the character Larry Gopnik (played by natural and rather obscure actor Michael Stuhlbarg) with far more dysfunctional people than him. This is where A Serious Man succeeds more than Beauty and Arrangement, in the opinion of this reviewer, because it is far more effective to satirize a person's inner struggles (and do a 'compare & contrast' exercise to other characters in the same story) than it is to spell out a sour breakdown of events.
There are many parallels made to the Book of Job containing a similar series of painful (but in Gopnik's case, also comical) trials to see if his faith in any way diminishes. Probably the most bizarrely silly scene is the film's prologue. It is yet another comparison made (more understandable with a second viewing) to trump the hero's crises as depicted later in the story. Striving to stay serious (and Gopnik is not the only character purported as intently serious), he could be far worse. The story, as well as this review, is full of so many parenthetical sonnets that they could inspire feature length stories themselves. This is probably the Coen Brothers' most metaphorical film since O Brother, Where Art Thou? Like that film, its period setting and historical context puts things into perspective, even in a humorous way. A storm is always coming, so LIVE with it.