The Novel Habits of Happiness (Isabel Dalhousie #10) by Alexander McCall Smith

The 10th book in this beloved author’s consistently bestselling series featuring his insatiably curious, ever-delightful Edinburgh philosopher and amateur sleuth who now takes on a case like none she’s had before: one with paranormal implications.
From a small town outside Edinburgh comes the news that a young boy has been recounting vivid recollections of a past life: a perfect description of an island off the coast of Scotland which he couldn’t possibly know, and a house there, where he claims to have spent his former life. When the boy’s mother asks Isabel to investigate his claims, she feels she must–of course!–help them learn the truth, and she and Jamie set off for the island. But finding the house the boy described only leads to more complicated questions. And when they learn the tragic story of the family who lived there, Isabel is suddenly faced with a situation of extraordinary delicacy that will require all of her skills both as sleuth and philosopher. (Meantime, back in Edinburgh: Will an elderly lothario take Grace away from Isabel? Would Isabel be able to manage without her stalwart housekeeper, companion and babysitter?)