Coming-of-Age
It's pretty hilarious that Amory Blaine is "puzzled and depressed" (3.2.167) by A Portrait of the Artist as a Young Man by James Joyce, because his own story is extremely similar to Joyce's. Yup, This Side of Paradise is a grade-A prime bildungsroman.
We chart Amory Blaine's growth from a selfish and narcissistic adolescent into a troubled (but potentially less narcissistic) young man. The novel observes him most closely through his college and post-college years, a time during which he—you got it—comes of age. He gets his adult on. He abandons childhood. He gets banged around a bit by life and emerges no longer a boy.
It's not as heartwarming as Little Women, and it doesn't have the rockin' soundtrack of Stand By Me… but never fear, This Side of Paradise is abso-freaking-lutely a bildungsroman.