Reading some books is like walking through fields of thistles. Struggling to walk through brambles and thorns sometimes while stepping over and around obstacles. Clothes and limbs bleeding when the end of the book is reached.
Reading other books is more of an adventure without the hardship. Reading each chapter is like balancing on moss covered stones in waist deep freezing water. There is the anxiety of remaining erect while at the same time daring the slippery stones to drop me into the cold water.
Some books are too tame for me. They don't cause me to think or use my imagination. I am just reading words. It only takes a few pages of reading to know this type of book is not going to hold my interest.
This scale reminds me of The Three Bears, porridge too hot, too cold, and just right. The books that interest me are somewhere between too hot and just right.