My Sister, the Serial Killer

This somewhat tongue-in-cheek novel by Nigerian author Oyinkan Braithwaite is really more about sisterly dynamics than it is about serial murder."One sister is a nurse. The other is a murderer." (NYT)
Ayoola is the favored daughter, the golden child of perfect looks and perfect temperament, according to their mother. Korede is the older sister, practical, smart and always charged with looking after her younger sister. Now that their father is dead (murdered?) the sisters live with their mother in the family estate that they cannot afford. Korede is a nurse at St. Peter's Hospital in Lagos and it is only there, in her job, that she gets any credit. Recognized for her competence and compassion, she'll soon be appointed as head nurse. Most of her colleagues are slackers, but Korede takes her job very seriously, especially because she has been secretly in love with Dr. Tade Otumu for several years and she keeps hoping he will finally figure out that they should be together.
When Ayoola calls on Korede for the 3rd time to help clean up one of her messes, i.e., a dead boyfriend, who she admits killing but totally in self-defense, Korede begins to realize that something is seriously askew in her sister. Still she cleans the scene, disposes of the body, and keeps quiet about what she knows--except to confide in a hospital patient who has been in a coma for several months. He is like her therapist--someone to talk to who does not judge. On impulse, Ayoola comes to visit Korede at work to invite her out to lunch. There she meets the kind and handsome Dr. Tade and he is smitten, later asking Korede for Ayoola's phone number. Talk about fraught love triangles! Now what will Korede do, protect her little sister or the love of her life? Darkly humorous, well written with vivid characters and setting. You get an accessible tour of urban life in Nigeria. A quick and engaging read. Rave reviews aplenty: New York Times, The Guardian, the Washington Post,  and Kirkus, plus a short interview with Scott Simon on NPR.