Susan is in her sixties and has made a life for herself in Watkins Glen, where her family spent the summers of her childhood while her father raced drag cars. That summer life came to an end when her parents died when she was a teenager, and she and her brother went to live with relatives. In adulthood they drifted apart.
Susan's life is interrupted by a phone call from her nephew, who is worried about his father, Susan's brother Mark. So begins a series of events which leads to Mark, who is in the early stages of Alzheimer's disease, coming to live with Susan. Her life is upended as she struggles to cope with his increasing confusion, his obsession with painting, and his belief in a strange monster living in the nearby lake.
This is not an easy read. Mark's deterioration is ongoing and unstoppable, and the moments of lucidity, where he and Susan are able to connect and make some sort of sense of their childhood together and their adulthood apart, make this all the more poignant. Both Mark and Susan are well-drawn characters, and I felt deep sympathy for both as the book progressed.
The prose is beautiful, as are the descriptions, but I did find that some passages were just too slow, and the whole thing felt repetitive in places. Although that probably added to the realism of the novel. 
On the whole, this was an enjoyable and enlightening read.
With thanks to NetGalley and Mayapple Press for the advance reader copy of this title.