I'm not one for reading a lot of writing books. Those I do read, I tend to dip into here and there. But I just finished reading Stephen King's On Writing cover to cover and absolutely loved it.
Part honest, unflinching memoir, part writing advice, this is not like any other writing book out there. I don't agree with all of what he says - I don't think any writer would, as we all have our own likes and dislikes, our own ways of doing things. But that's what's so great about this book - he doesn't try to say that his way is the only right way. It's simply a compendium of what he knows.
I really liked the blunt, no-nonsense style in which the book is written. SK gets the balance just right - he talks about the hard work it takes to be a writer without losing the sense of magic that drives writers to do what they do. Even if you're not a writer, I think you'd find this an interesting book, in terms of the insight it gives into the mind of one.