Last one and half month I have been studying pretty hard, after office hours . I have an exam scheduled next month. Since, i have long long work hour weeks and have very few hours for myself- i have decided to study as effectively and intensely as i can in those hours.
I am applying few techniques in my study-plan to get through some enormous amount of study material in small time and to retain them well in my brain. These techniques have been working pretty well for me:

1) Pomodoro technique:
I keep a timer when i study. I study in chunks of 25 minutes. In those 25 minutes, i am “dangerously present” in my studies. I listen to light instrumental songs in my headphone while studying. This helps in blocking the distractions. After a 25 minutes sprint, i take a 5 minute break. And then do another 25 minute sprint session. After 3-4 such sprints i take a longer break of 10-15 minutes. And repeat this process. Pomodoro helps me to focus intensely and get through atleast 4X more study materials

2) Learning from multiple mediums :
Its very difficult sometimes to understand complicated concepts only by reading. Hence, i try to consume information from multiple channels. I downloaded audio lectures for my study materials. I listen to them every day in my commute time to & from office-home. I listen to them when i go for a brisk walk or, even when i am in the gym. For things that i still have difficulty grasping, i watch videos on those topics on youtube. Consuming content from multiple source helps me to get “immersed” in my learning. This really helps.

3) Not learning alone :

Learning alone is just too overwhelming for me at times. Hence, i managed to get in touch with a few people who are in the same boat ,to talk to about my study materials. I also joined whatsapp, reddit, telegram groups- of people who are preparing for the same exam. Taking part in conversations about the exam contents, discussing solutions to questions helped me reinforce my learning, helped me learn from other peoples perspective.

4) Richard Feynman Technique:
There are four steps to the Feynman Learning Technique:

• Choose a concept you want to learn about
• Pretend you are teaching it to a student in grade 6
• Identify gaps in your explanation;  Go back to the source material, to better understand it.
• Review and simplify (optional)

So, while studying hard conceptions, i try to break it down to layman`s term and try to connect it with stuff that i already know. I also make notes while doing these.

5) Taking notes by hand :
I always made notes while studying. I take notes in paper and pen. The act of writing stuff down , creates more neurological footprints in my brain than writing in any apps. Hence, i always take notes .

6)Repetition , Repetition, Repetition:
When the volume of things to remember is so big, i find it difficult to retain all of the things that i have read. Hence, every night before going to bed, i skim through my notes. I also use flashcards from quizlet.com/cram.com . Spaced repetition really cements information in the brain.

7) Practice testing
One last valuable technique is practice testing, while learning. When i practice tests, it becomes clear which materials i really understand and which i dont. These pointers really help me to go back to the books and solidify my weak areas. And practicing tests, makes us better at giving tests. This really really helps.

I have applied all of the above technique in my study sessions to finish these books in last 45 days.
I hope some of these study hacks help you too.