Read loudly. When you read loudly the words enter through ears and echo within your mind. When you read silently you don’t remember for long what you have read. This is my personal observation. You can try and see if the idea works for you.
When you make a story with the written words, you remember the answer well. You need to draw a picture on your mind of what is being said or written. Then you would be able to relate well.
Also, keep revising. If you don’t revise, you tend to forget unless and until you have that kind of extraordinary brain. For average people like majority, revising what they have learnt is necessary.
Make notes and paragraphs of important points. Keeping only relevant items at one place will help you to concentrate on what is required rather than surfing through the entire book repeatedly. Study where there is less noise and distraction. Concentrate and win the game.
Last but not the least. Work hard and you will surely achieve success in your endeavours.