Always when I’m reading history books ot maths or any study book, when I close the book I forget everything, what should I do?
I take two different approaches to this type of situation, short term and long term!!
When you are reading a book and just want to hold on to the information of the book for short time(minutes to hours),you should just use the idea of ‘pegs/hooks/marker/grid/macunx’,etc!! These work like a RAM of a computer holding data for quick access and for a short period of time!! The technique is simple,but effective. Take a peg list that you know very well and start to connect what you have read with the list! After four to five peg lists association,review them. Then,create a new list… You can use objects of your room,too,instead of peg lists. For example,you can take your TV and associate two or three ideas that you have read in your book with the TV. Take another object that you are very familiar with and associate two or three ideas with it!! Mattias Ribbing describes the process very well in this video >> https://www.youtube.com/watch?v=GLQavCERL1M&t=2514s
Using this type of technique will increase your understanding of the subject you are going through and will increase your focus.
Then,if you want to keep the information for long term,start to use Memory Palace and other study techniques! For example,converting texts and symbols to memorable images,Spaced repetition,etc! This works like the HardDisk of a computer where we keep data for long term use!