I haven't read the book but I've just realised I've heard of it. It's written by Phyllida Law who is an actress and mother of Emma Thompson. Here is an article about it -
I have just read "The little girl in the radiator" by Martin Slieve which was written by a son after his Mother was diagnosed. I thought bits of it were a bit far fetched but overall it was a good insight into living with a person with dementia and getting a person in to care.