I've heard (many times) an illustration of a mango orchard (usually used to teach a dynamic related to evangelism) which goes something like this: In a mango orchard the mangos do not ripen all at once, but over many weeks. So, instead of harvesting by cleaning all of the trees, the worker has to continually go back through the orchard looking for ripe fruit. I don't know if this illustration is accurate or not, but it pretty well describes my experience with books. Some books I acquire and browse and set down for months or years (decades even). They just don't resonate, or I'm just not able to understand them. I might understand the words and sentences, but I feel impatient or bored. Later and pick them up and discover solid gold. C. S. Lewis has been like that for me. Some of his writings I read and enjoyed long ago (Screwtape Letters, Mere Christianity), others are just now becoming ripe.
From God in the Dock:
"Science progresses because scientists, instead of running away from such troublesome phenomena or hushing them up, are constantly seeking them out. In the same way, there will be progress in Christian knowledge only as long as we accept the challenge of the difficult or repellent doctrines. A 'liberal' Christianity which considers itself free to alter the Faith whenever the Faith looks perplexing or repellent must be completely stagnant. Progress is made only into a resisting material."