Adventure, Pastoral, Comedy, Romance
Neil's "voyage of discovery" from the city to the suburbs is presented as a bold adventure—even though, overall, the story features a pretty mundane and run-of-the-mill course of events. You can call the novella a pastoral because of the way it contrasts the crowded city with the idealized suburbs.
In some ways, it kind of reminds of us William Shakespeare's As You Like It. When Neil plunges himself into a new and strange environment (the pastoral suburbs), he begins to learn who he is and what he wants. He returns to Newark with a heightened degree of self-knowledge, which completes the pastoral cycle of voyage and return (see "Booker's Seven Basic Plots Analysis" for more on that).
The novella is also funny. It fits the requirement of a comedy by having a happy ending. By the end, Neil seems to have discovered that he belongs in Newark and he knows that his work in the library is meaningful and important to him. We should point out, though, that the novella isn't a romantic comedy. The love affair ends badly, without even a farewell kiss or a goodbye—the quintessential summer fling, perishing like the leaves on the trees once fall rolls around.