I am interested in accretion processes around black holes and so I am looking for some comprehensive resources aimed at beginning graduate level. I came across two review papers, Foundations of Black Hole Accretion Disk Theory and Accretion Discs in Astrophysics . Since I am at the beginner level, I couldn't understand many of the stuffs in those papers.
What are some good resources (books or review papers) that I can read to obtain sufficient knowledge to understand research papers?
I am mainly interested in Quasi-Periodic Oscillations (QPOs) and spectral analysis of black hole candidates.
I have basic knowledge of Astrophysics and General Relativity at Masters level and I am looking for graduate level references on accretion processes.