Regarding Ducks and Universes

On a foggy Monday in 1986, the universe suddenly, without warning, bifurcated. Fast-forward to 35 years later Felix Sayers is a culinary writer living in San Francisco of Universe A who spends his days lunching at Coconut Cafe and dreaming of penning an Agatha Christie-style mystery. But everything changes when his Aunt Henrietta dies, leaving Felix a photograph of his father and himself--dated ten days before Felix was born. It can only mean one thing Felix has an alter in Universe B. Panicked that his mystery novel may exist already, Felix crosses to San Francisco B and proceeds to flagrantly violate the rules of both worlds