If he was 57, then the book's probably from 1922. Harding checked out in 1923 at the age of 58.

Wikipedia: The doctors issued a release stating that the cause of death was "some brain evolvement, probably an apoplexy." Modern doctors say it was probably congestive heart failure. Of course there were speculations he had been poisoned by his wife, since he had a few affairs in his day. And night.

"These women included Susie Hodder and Carrie Fulton Phillips, Mrs. Harding's personal friends."

Cad. There was also the strange case of Nan Britton, if you wish.