The Sunday Philosophy Club by Alexander McCall Smith.
A well-to-do moral philosopher in Edinburgh and the editor of a journal called Review of Applied Ethics, witnesses the death of a young man who falls from the higher rows in a concert hall. She, effectively, is the last person to see him alive as he falls, and feels that she has a moral responsibility to investigate his death. Enlisting the help of her niece's ex-boyfriend, who she herself is half in love with, Isabel tries to probe whether the death was accident, suicide, or murder. At the same time, she tries to get her niece's love life in order, though not with any degree of success.
The mystery isn't much to write about; what comes alive in Isabel's journey is the deep moral choices we face, and more often than not, choose to avoid--telling the truth vs. lying, forgiving vs. punishing, and so on. The slices of philosophy fit interestingly into satirical comments about Edinburgh culture and society and quiet insights into the human condition.
Though several parts of the book were quite interesting, one that stayed with me is set on a bus journey that Isabel makes late at night. The other people on the bus are a man in an overcoat who seems oblivious to his surroundings, a couple absorbed in each other, and a teenager trying to make a statement with his attire:
"Isabel smiled to herself: a microcosm of our condition, she thought. Loneliness and its despair; love and its self-absorption; and sixteen, which was a state all its own."
Another interesting part was Isabel's conversation with a man who has piercings all over his face. She wonders how any girl would like to kiss this guy, and so forth, and then asks him why he has these piercings. That's quite a philosophical conversation too.
Our moral dilemmas and Isabel's perspectives on them make for just the right kind of reading--thought-provoking but not self-consciously so, warm but incisive, leaves you with a smile, but also with several questions.