When I was little, my mom encouraged me to read because it would help my vocabulary scores on the tests that we took at the end of each year. Eventually, that helped on the SAT as well. It had a funny side effect though. Because I read so much, there were words that I knew how to spell and I knew what they meant, but I had never heard them in speech so I didn't know how to pronounce them. For example, I thought Poland, the country, was pronounced "Pahland" until I was about 13. I also thought the word sleuth (from my Nancy Drew days) was pronounced "slehth."
Aside from those pronunciation mistakes, I always had the intuition that carefully reading quality writing would help me become a better writer. Prose's book has articulated that, and she uses passages from classics to demonstrate her points. I'd recommend it for people who love language and want to learn to use it well. Here are parts of the opening passage from the book:
"Can creative writing be taught?
"It's a reasonable question, but no matter how often I've been asked it, I never know quite what to say. Because if what people mean is: Can the love of language be taught? Can a gift for storytelling be taught? then the answer is no...[but], a workshop can be useful. A good teacher can show you how to edit your work. The right class can form the basis of a community that will help and sustain you...Like most -- maybe all -- writers, I learned to write by writing and, by example, by reading books."