I've read this a couple of times and always find it helpful, useful and often find something new that I missed or is just now making sense. She advocates 'careful reading' and provides tons of examples and excerpts from well-known books. I've had the hardback for a while but just noticed that there is an ebook available and so purchased it last night. So much nicer to have my useful books in ebook form!
(it is almost worth the price for the "Books to be Read Immediately" list at the end/appendix to the book.
P.S. Since the target appears to be writers I posted this here, but it just as readily applies to serious readers as well.