This film isn't merely serious; it's grim.
It's a dark comedy without the comedy.
And if the Coens mean for us to take it seriously, I feel they've miscalculated.
I agree with Joe Morgenstern in the Wall Street Journal.
Here's some of what he said about this ultimately senseless film:
"A Serious Man," written and directed by Ethan Coen and Joel Coen, asks the most serious of questions—what does God want of us? I would add a question that isn't so serious, though it isn't frivolous either. What do the Coen brothers want of us? More specifically, what do they want us to think of the repellent people in this pitilessly bleak movie?
As in so many of their earlier films, the Coen brothers create comic caricatures with broad performances, grotesque traits—Larry's brother has a sebaceous cyst that never stops draining—and leering, wide-angle shots that invade their characters' personal space. (I've often felt they're invading my space too.) This time, though, there are differences. Their movie is strongly, if not literally, autobiographical, and their caricatures range from dislikable through despicable, with not a smidgeon of humanity to redeem them. Are we meant to loathe these people too, or did the filmmakers fall victim to their customary technique? If the latter, what a miscalculation. If the former—if "A Serious Man" reflects the brothers' feelings about their roots as well as their god—then some of those earlier films may have been more misanthropic than we knew.