Final answer:
The book that the narrator read to Roderick Usher was 'Mad Trist' by Sir Launcelot Canning.
Step-by-step explanation:
The book that the narrator read to Roderick Usher when the parallelism occurred was 'Mad Trist' by Sir Launcelot Canning. Although the narrator described it as a favorite of Usher's in a sad jest, it was the only book immediately at hand. The narrator hoped that reading the book would provide some relief to Usher's mental disorder.