The ideas will begin to stick once you have the opportunity to see the positional patterns unfold themselves in your own games. In other words, I don't think you will maximize your benefit from reading by simply trying to remember the ideas demonstrated in the game examples provided in the books.
As you play your own games, make it your first goal simply to recognize any of the positional patterns you have read about. If you can think about your next move based on the priniciples of the books, that is even better. However, first recognize the patterns. After the recognition becomes automatic, then the intuition for how to play the position soundly will develop through your knowledge of the game examples in the books.
I have 2 chess books which I am reading at the moment, but I am not sure how to use them appropriately in order to retrieve the most knowledge from them. I am reading My System by Aron Nimzowitsch and The Amateur's Mind by Jeremy Silman. At the moment, I am just reading what they are saying, trying to follow the games in my head but I am not sure many of the ideas are sticking. Help please!