Seriously? Not to give too much offence or anything I was guessing 11-13 when I saw that... If you go to Barnes&Noble or Boarders Books they have art sections with a fairly good selection, for beginner intremediate and even a couple of advance-ish books. Though I'll tell you now the majority of it is "how to draw manga" crap. I'm not sure if you are going for a manga style here, but if you are guess that's a good thing. A good book would be cutting edge anatomy, which does an excellent job of teaching anatomy. And if you are going for manga, there are about a hundred books there that will teach you beginning stuff. I mean, you are a bit behind for your age, but if you work hard you should be alright. Especially if you want to draw manga, that
crap stuff is easy.