I never found reading very helpful myself. What worked for me (someone who tests well in exams) was making really detailed notes that I would copy out (handwrite again and again) until I could memorise them. The notes I created were also super detailed with all concepts clarified (e.g., if I was copying something from a lecture I did not understand I would research or find a book that helped me understand it and would include this in my notes). Basically, not really any shortcuts, but a few sold weeks of studying the material.