I'm currently reading Lady Rosamund and the Poisoned Pen by Barbara Monajem. This book is the first in the Rosie and McBrae Mystery series.
Lady Rosamund Phipps is a bit different. Her best friend happens to be her husband's mistress. The situation suits Rosie perfectly as she has no interest in carnal desires and is happy that she gets along well with her husband and is away from her domineering mother and older brother. Rosie also has a secret. She feels the need to check things over and over again. Her mother and brother believe she teeters towards madness and at any moment could bring shame to the family name. After discovering the dead body of a footman, Rosie becomes a favorite subject of the anonymous caricaturist, Corvus. While she thinks it funny, her politician husband does not. Soon she starts receiving anonymous letters threatening to reveal her secret. But, who could possibly know? Rosie decides to discover the true identity of Corvus, that revelation surely taking attention away from her. But can she trust her husband to stand up against her mother and allow her to remain in London? Is that Scotsman a friend or foe? Will she find the answers she seeks, or will the threatening poison pen letters send her over the edge?