Every book you read makes the next one easier to understand. Knowledge stacks like interest.

Knowledge builds on itself. Each thing you learn gives you more hooks to hang the next thing on, so the tenth book on a subject goes down far more easily than the first, and understanding speeds up in a way that is not obvious at the start. Early reading feels slow because you are building the frame.

If something is hard going, stay with it a little longer rather than deciding it is not for you. Read two more on the same subject. The difficulty usually belongs to the beginning rather than to the material or to you.