I'd like to learn more about brewing, but am not concerned with the basic mechanics as I've been doing all grain for several years. What are some good books on creating your own recipes, improving/better understanding your process, or even just improving your understanding of the different characteristics of beer?
EDIT: After reading Good Subjective Bad Subjective I'll attempt to better define the question. I'd like to know specifically how to approach creating a recipe with a style or specific example in mind, including things like selecting ingredients, determining mash schedules, fermentation temperatures, etc. Ideally I'd like to know specifically how a book has helped a more experienced brewer (lets just say more than a couple brews).