Books change the mind. Writing, too. But in constructive idleness your mind writes the story. Read afterwards. Write afterwards, but do not burden your mind with the words of others.
Do books qualify for proper idleness? Even if they are relaxing pulp? No. They keep the mind working, occupied and are creating purpose. That is indeed very good on the one hand, but giving your mind a break in doing nothing properly, you create something new for yourself on the other hand.
Related Work
Flatness of life?
You think water moves fast? You should see ice.
Calculations, worries? Have a tea!
Why calculating risks and worrying too much. Make time for yourself!
TV, MOVIES = distraction
You watched the movies we put in? Why? They do not tell you anything. That is how you surf sometimes.