Murder Under A Blue Moon by Abigail Keam

Book 1 in the The Mona Moon Mystery series

There’s a knock on the door. Who could this be in the middle of the night? Holding a revolver, Mona reluctantly opens her door to a man wearing a Homburg hat and holding a briefcase.
“I bring glad tidings. Your Uncle Manfred Moon has died and left you as his heir to the Moon fortune. You are now one of the richest women in the country!” he says.
Mona’s response is to point her revolver in his face. If the stranger is telling the truth, she will apologize. If he is a fraud, she will shoot him.
That’s how Mona does things in 1933.

“Readers who enjoy witty historical mysteries will love this brand new series!” Kate Carlisle, author of the Bibliophile Mysteries and the Fixer Upper Mysteries.