The Alienist by Caleb Carr

In 1896 in New York City, a serial killer is on the loose.  Police Commissioner Theodore Roosevelt calls in two of his Yale buddies to help solve the crime.  One is Theodore Kreizler, the brilliant and unorthodox alienist (psychologist).  His research on the criminal mind and his belief that many of the worst criminals can be rehabilitated has made him famously controversial.  The tension rises as more and more young boys from New York City's seedy night life are gruesomely murdered.  The historical references and city sites made this seem like a real life crime story.  The nature verses nurture psychology debate is also an interesting background story.  At the core this is a fascinating tale but I think it could have been about 200 pages shorter.