First, you should take care of your health and body and mind first and foremost.
Second, we all have different learning styles and all universities have different formats for QPC exams. Match both.
HOWEVER
If you don’t have the time/possibility to do full books, read book reviews (SEVERAL) and use..
But more than anything...
Learn to mind-map the connections between authors, themes, concepts, paradigms, etc.
Write by hand in index cards (try it and trust me).
And good luck!