The Graduate is different from other "Coming of Age" movies and books, since Benjamin is a little older. But even though Benjamin's a college graduate and therefore supposedly prepared to face the world…he really isn't prepared to face the world at all. He thinks that rebelling against his parents might be the key to maturity, but it doesn't quite work out that way.
The movie's a comedy-drama, since it has plenty of comedic moments along with more dramatic ones, and a greater, more serious point. Benjamin's bumbling steps away from and towards his seduction are played for laughs, but other parts of the movie have a much more serious tone. There's the scene when Benjamin runs into an angry Mr. Robinson whose marriage has just ended; and the ending scene when he and Elaine escape the wedding, only to have their expressions fade from joy to uncertainty on the city bus.
Additionally, you could make the case for the movie as satire, since it pokes fun at Ben's rich SoCal society—a world where an Alfa Romeo Spider is a normal graduation gift; where people give unusually dispiriting career advice about the plastics industry and bored housewives seduce their friends' sons.