The first book that Earl Grayson reads cover to cover is "The Little Engine That Could." That sounds like Earl Grayson read that book when he was a young boy, but that is not the case. As a young boy, Earl struggled to read, and teachers simply gave up on him.
"This bunch will never learn to read a stop sign."
Maniac learned that detail in chapter 27, so Maniac took it upon himself to help Grayson learn to read. Grayson is an old man by this point. Chapter 28 starts by letting the reader know that Maniac must be meeting some success, because the first sentence announces that Grayson read his first book cover to cover. Reading "The Little Engine That Could" was not an easy task for Grayson. The text explains that it took him just about an hour and left him sweaty and exhausted. That sounds rough, but it shows Grayson a success, which he hasn't had a whole lot of in his life.