I don't think I worded the title properly, theory sounds a bit wrong. Anyway I wanted to know about more books that discuss more than just art or drawing techniques. I've read Vernon Blake's the art and craft of drawing and although some of it was probably beyond me at the time I still enjoyed it. I also started reading Edward hill's the Language of Drawing though this book has raised more questions than I am probably ready to deal with. Also I heard some good things about Nathan Goldstein's books. So does anyone know of any other books like this?