Jean I: Rightful King of France

In a strange footnote to the Hundred Years' War, a Sienese merchant named Giannino di Guccio came to believe that he was actually King Jean I of France. A new book, translated from Italian, he Man Who Believed He Was King of France by Tommaso di Carpegna Falconieri, tells the story.

The New Yorker has a brief review of the book:

"Falconieri painstakingly pieces together the events surrounding his hero’s doomed bid in a narrative that reads like an adventure story."