Nick is referring to Henry Clay’s Economics: An Introduction for the General Reader.
Ray C. Fair offers an interesting consideration of Fitzgerald’s inclusion of this book here. As it turns out, this book wouldn’t have been used at Yale while Nick attended.
Henry Clay is a famous supporter of the American System.
Gatsby is keeping himself busy while he anxiously waits for Daisy.
To help improve the meaning of these lyrics, visit “The Great Gatsby (Chapter V)” by F. Scott Fitzgerald and leave a comment on the lyrics box