Getting into arguments...

I have always believed that everything that is worth writing (or worth reading) has an argument, a main purpose for having been written, a main point that it strives to communicate.

I am sure that you probably learned in high school, or even a freshman composition course, that an essay must have a thesis, which should be a statement of its argument, but you’ve probably never thought how that rule should also apply to other forms of writing as well.

Yet it does. All good writing must have an argument, and therefore a thesis of some kind.

That being said, poems and novels, of course, go about constructing their arguments differently than a five paragraph essay (and it's a good thing, because if poems were anything like five paragraph essays, I would not have any interest in reading or writing them), but it's primarily a difference of form, not content.

The thesis of a literary work isn’t going to be as explicit as an English 101 essay, but rather will be implied. Nevertheless, literary works need theses as much as any other kind of writing.

You might consider thinking of a poem's argument as analogous to its meaning (although there's nothing deep and hidden about it—the only thing between the lines is empty space, and perhaps the reason we're so afraid of poetry is that it's been mystified to death by a bunch of meaningless clichés).

In any case, if you practice reading poems (and novels) for their argument, you'll start to get pretty good at it. You'll also get pretty good at reading most everything else.