Most of the Zen sermons many of us read are taken from the discourses of the Buddha, the treatises, and the commentarial literature. Zen teachers were not trying to be original in composing their sermons. They had no reason to be. The greatest difficulty for them when they began their journey was seeing what the Buddha saw under the Bodhi-tree. We call this kensho in Zen. Without it Zen turns into an inferior Zen dominated by sitting. This kind of Zen doesn't spend too much time trying to understand the sermons of the Zen teachers or the Buddha. The reason for this is the problem of reading comprehension.
This problem is really a distinct kind of learning difficulty which in Zen Buddhism can be difficult to overcome without help—and help doesn't come easy if at all. This is why treatises and the comments to various treatises are so important. They can teach the budding adept how to comprehend the necessary material. At the same time there must be present the overarching will to see what the Buddha saw, awakening to the unconditioned absolute in the time of the blink of an eye.
Rather than comprehend what we read it still seems much easier to just sit than to think. But thinking is important. By it we learn the context of Zen and also the direction Zen wishes us to look that we might one day find our true nature.
When I look at the old books in my little library that I struggled through many years ago, and now find it easy to understand them, I think I have learned what reading comprehension is about and how difficult it is for those who sincerely wish to study Zen to increase their reading comprehension skills.
I found it easier to understand what I was reading when I was alone with a kerosene lamp, with silence in the background. There was no music except maybe the sound of wind. There was also the warmth of the fire from my Fisher stove. It was by meditation that I was able to silence my monkey mind so that I could comprehend better. Nor did I shy away from difficult passages. I went back to them hoping that one day I would understand them. I carried them with me you could say.
It takes a long time to increase Buddhist reading comprehension. One, above all, has to have patience. Truth doesn't come easy.