Arcane Casebook book 1, but stand alone. A private investigator and rune-wright in a magical New York 1930s.
Alex is on the job, having just managed a case, and the police call him over. They have a burned body on their hands. Alex deduces a few things that lead them to use a powerful rune that reveals more complications. Then, he goes to help at a church mission where he had found refuge when a child -- helping with the roof tiles against the leaks -- and returns to his mentor's home.
That is where he get called back to the mission. And the plot thickens.
It involves rivalries between sorcerers, helping a girl get a new job, a woman whose brother didn't arrive for a dinner, a pack of cigarettes, the rune needed to restore a tooth, life runes that you have to die younger to use, and more.