Some years ago, I read three excellent novels via my local library. The author is Ingrid Noll and the books are dark, yet full of black humour. Most amusing of these is the first, in which the main character is in her 50s, so nobody takes any notice of her. She therefore, "gets away with murder". As I can't remember many of the details apart from having enjoyed the novels, I reprint here the publisher blurbs (unfortunately not revealing the name of the translator), which come with a recommendation from Val McDermid:
Hell Hath No Fury: When 52-year-old Rosemarie Hirte falls for Rainer Engstern, she knows that this could be her last chance for happiness. Finding herself in the grip of terrifying obsession, Rosemarie spins a deadly web in which she lures and then destroys all those who come too close to the object of her love.
Head Count: Maya's only memory is being at odds with her mother and brother. Her father seemed to love her but he disappeared. Maya's life is embattled until she meets Cora. The two form a friendship founded on a conviction that they are somehow separate from society and do not have to abide by its rules.
The Pharmacist: A gripping psychological mystery from one of Europe's best-selling crime novelists. Would you confide your most intimate secrets to a stranger? Hella Moormann, a pharmacist, finds herself doing just this when she meets the unprepossessing Rosemarie Hirte in hospital. Hella has always suffered from a need to nurture lost souls, but she believes her latest lover will be different. Levin, a beautiful young dental student, is heir to his grandfather's fortune and looks like a good thing. All too soon, though, her faith is shaken: not only does he take an unhealthy interest in some antique poison bottles, but he also plans to misuse his dental skills in a macabre way. Hella's life takes an increasingly bizarre course, from involvement with drug runners to murder, via adultery and much else. But is she the helpless victim of fate or a cunning manipulator of events? Whatever the truth, in choosing to tell her story to the anonymous Rosemarie Hirte, she may have made a lethal mistake, for Hirte has a sinister secret of her own…
From Wikipedia: Ingrid Noll has written several novels, including Head Count, Hell hath no Fury and The Pharmacist, as well as one television drama, Bommels Billigflüge. Several of her novels have been subsequently adapted as films, including Die Apothekerin, which was released in the United States as The Pharmacist and was nominated for the German Film Award in Gold for outstanding feature film. She wrote her debut novel at the age of 55 and is (says Wikipedia) one of the most appreciated authors in Germany.
DW-World interview with Ingrid Noll, who describes herself as: "good-natured, usually easy-going and easy to be around, loyal, I have a good appetite, and I'm sometimes a bit venomous." It's a very funny (and short) interview, and I strongly identify with the final answer.
Ingrid Noll at the Internet Movie database, from which it appears that she may have written some more novels and adapted them for film and TV.