I would go with the book. It is far superior to this lanquid and super violent limited series adaptation. The cast is uninspired. Unless you can’t live without seeing one of the best reproductions of New York City at the turn of 20th century, read Caleb Carr’s humdinger of a novel.

https://en.wikipedia.org/wiki/The_Alienist_(TV_series)

https://en.wikipedia.org/wiki/The_Alienist