The concept is very interesting, and the author does execute it well in parts, but I don't think the concept holds up enough for a full length novel. The repetition and mulling over the protagonist does as part of her dementia gets tiring to hear again and again. It kind of sent me a little batty. I really wish the author had written this as a novella; I would certainly like it a lot better, rather than wishing I could. 

(My favourite part of the book was the narrator. She was the only thing making me finish the book. I really hope they paid her very well for all that going back and repeating.)