The main idea is to create an endless soundtrack so that every part of the song is connected to a simple memory. The soundtrack can be based on musical notes that are dictated by the digits of an irrational number.
An irrational number can not be expressed as a ratio of two integers. When an irrational number is expressed as a decimal, it will have an infinite number of digits after the decimal point. Examples of irrational numbers are Pi, Euler's number, and the square roots of natural numbers that are not perfect squares.
The series of numbers can be used to create music or sound signals that will be played when the user studies. New e-books can be published with a default music series during production while older books can be paired with a random soundtrack. The use of these sensations can be extended to improving one's memory of real-life situations. Since the sound is endless it can be played at all times and the sound associated with a particular point in time can easily be deduced and replayed when you want to recall what happened at that time.
Another thing that can help the retention of memories is how funny the thing is. E-books can be designed to have more interactive, funny parts. For example, some of the alphabets can be cartooned to show expressions on their faces. F=ma will be easier to remember if the "m" was sleeping or the "a" sneezed every time you look at it.