"Confessions of an Advertising Man" is a book by David Ogilvy, which was released on December 31, 1962, about the rigors of the advertising industry.
Action takes place from July 20, 1963, the day of the solar eclipse, until July 23, 1963.
When Peggy mentions she's read Conrad Hilton's book, she's referring to his 1959 autobiography, "Be My Guest."
The song that plays over the credits is "Sixteen Tons" which was a gold record and a Billboard chart #1 hit in 1955 for Tennessee Ernie Ford. It tells the story of a coal miner who works for a company who mercilessly takes advantage of his labor, takes everything from him, and how he can't get ahead. "I owe my soul to the company store," is evocative of abusive employment arrangements, like sharecropping, where workers had little recourse but to annually rent tools and buy seed on credit from the company store owned by the landowner. The sharecropper was required to pay back the store from the harvest--and after paying rent, other living expenses, and the debt from tools and seed--typically still owed a debt to the plantation owner at the end of the season. This, and other oppressive Jim Crow Era policies which left workers "another day older and deeper in debt," are why sharecropping is widely regarded as slavery by other means.