We can tell right off the bat that this is a Shakespearean sonnet. That form (14 lines of iambic pentameter with the last two lines rhyming) is a dead giveaway. There are lots of different themes in Shakespeare's sonnets, but they share this playful and sweet tone. Shakespeare can have fun, toy with our ideas, play with the words, and finally bring us back to a really sincere and important point. Check out how he does this in the last two lines of this poem. He's been fooling around, mocking other poets, when all of a sudden he drops a real confession of love on us. Long story short: Shakespeare is the master.