Maybe a bit more towards 3.5 stars...

Do you know Elvis Costello's Veronica? This is the book-length version. With a bit of Memento thrown in for suspense. The great thing about this book is how sensitively it depicts a woman succumbing to dementia - the confusion, the embarrassment at admitting to forgetting, the attempts to avoid that embarrassment by figuring out what's going on based on cues from the environment, the frustration that may lead to aggressive behaviours. The book has a sense of humour about it all, but at the same time gets the reader to feel a bit ashamed about laughing, because we can really empathize with Maud when she's faced with her sighing, eye-rolling daughter.
The not so great thing about this book is that it should never have been as long as it is - it becomes repetitive at some point, and there's a sense that some fairly big chunks could have been edited out without losing anything of significance.

But frankly, it's worth reading this book even if you give up two-thirds of the way it, just for the depiction dementia.