The speaker opens with a warning: "A great evil I saw." What follows is a small, strange parable. A book arrives to give people stairs, a way to climb and rise. But the people don't want to climb. They lift their heads to be kissed rather than to kiss, as if they expect to be honored, not to give anything back.
Because the readers hold themselves so passively, the book finds a different audience. Bonfires "desire" it and read it "with pleasure," which is a bitter twist: the only reader who truly takes it in is the fire that destroys it. The title, "Book of Martyrs," hints at people burned for what they believed, so the book may be both a victim and a record of victims.
The mood is dark and fable-like, close to a lament. The final image of the city as a "long night" suggests a place where knowledge goes unused. That's an interpretation, but the poem's tone supports it.