Your problem was with some me.i am feeling that how can i memorize these books at a longer time. So i had started the solution of my this problem. I had searched at least 3-4 months on internet, read the books. then solution is that do study in this manner:
1). First only understand the concept.
2).Revised it next day.
3). Repeat it after 7 days.
4)Again Repeat it 1.5 month.
and last when it is required.
I promised u my friend you will not forget any time in your life of that topic.its my practical Experience.
Also do yoga and mediatation 15 minutes.
Go morning walk for 20 minutes.
I read income tax on this basis.