"To Autumn" is probably the most straightforward of Keats's Great Odes. It does not contain any references to Greek mythology or complicated metaphors spanning five stanzas. The main challenge with Keats is the density of his images. You can't skim a poem like this, but then again, why would you need to: it's only three stanzas. When you slow down your pace, you recognize the little things, like the comparison of a flower to a monk's "cell" or the connection between the choir of gnats and the death of daylight. These small connections are what makes the poem great, so you don't want to miss out on them. Also, look for hidden patterns, like the use of rhetorical questions.