Final answer:
The irony in "April 2005: Usher II" lies in the fact that a society that has forbidden imaginative literature is ironically subjected to living out a story akin to Edgar Allan Poe's works, which they have banned, without their realization.
Step-by-step explanation:
The irony in "April 2005: Usher II" from Ray Bradbury's The Martian Chronicles refers to the situation where a society that has banned imaginative literature is now unaware that they are living out the plots of the very stories they've tried to suppress. In the story, a character creates a house that is an exact replica of the House of Usher from Edgar Allan Poe's tale. The government body responsible for banning the imaginative works, including Poe's, sends an investigator who fails to recognize the references to Poe's literature that the house embodies. The ultimate irony is that the investigator gets pulled into a recreation of the Poe story and meets his end in a way that mirrors the fate of characters in the banned works, completely oblivious to the literary significance of his fate.