The Hitch by Sara Levine

Rose is thrilled when her brother Victor and his wife Astrid let her take care of her six-year-old nephew Nathan while they go away to Mexico for a week. Rose can't wait to spend a lot of time with Nathan, since they usually only see each other for a few hours on Saturdays. However, soon after Victor and Astrid leave, Rose's dog Walter kills a corgi at a park and Nathan tells Rose that the corgi's spirit is now inside of him. This incident, of course, unsettles the quirky and judgmental Rose as she attempts to make things right, i.e. exorcise the dog. A novel, at times humorous, about love and familial obligations.