The speaker is a devoted reader, so absorbed in books that they become a kind of maze. Each story leads into another, and it's easy to lose the way out. Reading offers a glimpse of "another impossible life," one where nothing happens except out of passion. There are no chores, no obligations, only desire driving every action.
The images in the middle of the poem, "one fire / one green night," are compact and a little mysterious. Fire suggests intensity and warmth, while a green night suggests something dreamlike, maybe a forest or a world seen through the page. Together they make reading feel both thrilling and slightly otherworldly.
The ending shifts the mood. The speaker admits they "must expect to go dark / or be overrun." That sounds like a warning. Total immersion may burn out, or the stories may swallow the reader whole. The feeling is love mixed with unease: wonder at what books give, and a quiet worry about what they might cost.