Yoga, chakra, and other related books

I'm looking to order some books to get deeper in my learnings about Yoga. I love yoga but currently only do it at home and want to begin going to classes a few nights a week and eventually become an instructor. A friend of mine set me up with a consult with an instructor in my town to see if she feels I'm a good fit to "shadow" her and learn more but I also want to make sure I have my own knowledge to bring to the table once I'm there. Thank you (: