In my opinion, the two young men discuss literature because their discussion shows that they are something of dilettantes. It shows that they are really pretty shallow.
In this story, the two of them discuss baseball, literature, fishing, and Marjorie. This is a pretty wide range of topics, but they don't really seem to know much about either baseball or literature. They are just kind of talking superficially about those things.
To me, this goes along with how they act when they're drunk. When drunk, they try really hard to show that they're practical. So when they talk, they try to show they know things when they don't really. When they act (while drunk) they try to show they're competent when they're really not.