I swore off difficult men after writing Robert Mapplethorpe’s biography. When my book was published 25 years ago, it elicited violent criticism from some of his friends. They felt I’d been too hard on the controversial photographer whose S&M pictures had created a firestorm in the early 90s. One bombarded me with profanities. Another threatened to kill me. My publisher wondered if I should hire an armed guard.

When an editor floated the idea of a novel about Beethoven, my first thought was, “Another difficult man.” My second thought: “At least all his friends are dead.”