The List of Unspeakable Fears by J. Kasper Kramer
This spooky, historical fiction middle-grade novel takes place in 1910 in New York City. Ten-year-old Essie and her mother are moving from a crowded tenement in the Bronx to North Brother Island in the East River, where her new stepfather, Dr. Blackcreek runs a quarantine hospital for mostly poor immigrants who have incurable diseases.