I don't know if this book will help people be better writers. However, I do think it will encourage people to slow down a bit when reading literary classics, and to pay attention to more than just their plots.

It is true that Prose doesn't really talk much about genre fiction (except for a couple of references to Raymond Chandler) but I think that's fine. She writes what she knows, and there are plenty of other studies of what makes genre fiction great.