It’s A Mod, Mod, Mod, Mod Murder is the first in the Murder A-Go-Go series by Rosemary Martin (pen name for Rosemary Stevens). It has dropped to $0.99 as a US Kindle Countdown deal, good for about 5 1/2 more days from today (March 15, 2021).
Stevens wrote a number of Regency romances in the 1990s, then she crossed over and wrote four historical mysteries, also set in the Regency period, featuring Beau Brummel as the protagonist. She won an Agatha Award for Best First Novel for the first book in that series. And then she really switched gears and wrote three mysteries featuring Bebe Bennett, an executive secretary in the 1960s. I’ve read all of the mysteries, which are quite cozy but fun, and a couple of the romances, which I also liked.
Buy at Kindle US