I am a graduate student who wants to begin to get into Quantum Gravity. I've looked on internet for bibliography and I've found a lot of great books, but I would like to start from the beginning (of topics related to quantum gravity, the general relativity and quantum mechanics basis I already have). I'm not looking bibliography of any particular quantum gravity theory, but something more global, like an historical overview, the current state or, if I may ask for too much, any book describing how such theory should be. Also, I'm looking for formal bibliography, not for-all-ages books.
If anyone who's adept into this topic could help me, I would appreciate it so much.