Reading Like a Writer is the first book on writing that has made my head buzz in the same way my lit courses in college did. Prose dissects classics topically in various chapters, i.e., her first chapters (2-4) are "Words," "Sentences," "Paragraphs." I'm still reading it and plan to re-read it after I finish.
One major plus for me and where I am in life right now, is that it has rejuvenated my reading. I'd been getting lazy - just reading books for the fun of it and not really thinking about them, figuring I'd pick things up by osmosis. Sure, I do pick things up that way, but I learn so much more if I ask myself why I like something I read, or dislike it.
I guess the short form of what I'm saying is that the book teaches/refreshes how to read attentively. Something it's easy to forget when the pressures of playdates, school schedules, picking fuzz off your sweater and realizing it's dried snot (and not your own), take over.