Symbolism, Imagery, Allegory
Pop quiz: who (or what) is lazy (1.1), secretly worried about being provincial (1.1), uneducated (2.1), penniless (3.1), petty (4.1), rather naturally unappealing (8.22), a failure (8.29), obsessed with rank (9.1), has an injured ego (9.1), delusions of grandeur (12.1), a severe persecution complex (18.1), and pitiful (20.1)? If you said, "Why, it must be Russia in the 19th century," you're in good company. That's a common allegorical interpretation of this story. After all, that's what many Russians were thinking about their country at the time.
The Russians' self-image hadn't always been so negative. It had been pretty good for about a century: Russia had been going through some serious reforms to make it more modern (and "European"). And when Tsar Alexander I defeated Napoleon in 1815, Russia became more popular in Europe. So far, so good, right?
Fast-forward ten years, to a very cold December in 1825. Goodbye, Alexander I (typhus). Hello, little brother Nicholas I. Some soldiers (later called the Decembrists) don't want Nicholas I to rule, so they revolt. Little brother Nicholas I crushes their revolt and proceeds to turn into "Big Brother" by taking away a lot of freedoms, and introducing a regime of repression, censorship and surveillance. Fast-forward another ten years, to the time Gogol is writing "The Diary of a Madman," and Russia is a lot like the Poprishchin character of his story.
Gogol eventually became a die-hard tsarist who even published a whole book to defend things like autocracy and serfdom (titled Selected Passages from Correspondence with Friends). But that was published in 1847 when he was a little older. So we leave it up to you to decide: can we read "The Diary of a Madman" as "The Diary of a Mad Country" or not?