In my advice on Topic Sentences, I’ve long advised students, both as readers and writers, to understand how a series of topic sentences often form a summary of a longer story or argument:
The first thing to notice is that strung together, the topic sentences summarize the passage as a whole. If the whole article is written in this way, then a reader can zip through the piece by reading only the first sentence of each paragraph, choosing to read full paragraphs only when she wants to know more about the claim made in the topic sentence. Few if any books an articles are written entirely in this manner, but in most cases, one can get the gist of a paragraph by reading the first two sentences, or the first and last sentence. Aim for the same kind of summary.
In fall 2019, a student introduced me to a lovely term for this device: the “topic-sentence poem,” which she had learned from her teacher, Dr. Cynthia Schafer of the Walker School of Marietta, Georgia. Henceforth, I’ll be teaching this as “Schafer’s Topic Sentence Poem.”