Hello! I have done some quantum mechanics, quantum field theory and general relativity. Not much, but enough to say that I have the big picture. Aside from this I have read about analysis on manifolds, functional analysis, Lie algebras and topology. Now there is a red book in my bookshelf that goes by the name of Spin Geometry by Lawson and Michelson and it is still to complex for me to grasp what it is about. This leaves basically two questions, i) What is spin geometry, does it have anything to do with quantum gravity? ii) Lets say it is a really interesting subject, is there any easier introduction to the subject that I should start with instead? Have I missed any important mathematics that I should grasp before?