Hi everyone. I'm a sophomore now , majoring in astronomy, and will become junior in no more than 1 month. I have a good command of classical electrodynamics and quantum mechanics. However, I'm confronted with some problems. 1. I want to know more about Astronomy. I borrow Very High Energy Cosmic Gamma Radiation by F.A.Aharonian from my tutor, but it's too difficult for me, because I know little in astronomy. So I want to find some fundamental books to read.. 2. I want to work on theory in the future. But I do not have a preferred subject. So I want some books which can introduce several fields (for example, Supernova , galaxy and so on)in astrophysics(or, cosmology) By the way, do I need to study QED QFT and GR? If so, when?