Books, and the amount of individuals who could read them, have been definitely vital to human development over the centuries.
It is necessary to bear in mind that, although plenty of the best modern books of all time tend to be regarded as ground-breaking works of fiction, for most of humanity's literary history, we did not write much fiction at all. Many stories would have been sung throughout the great majority of history, just since the large majority of people could not read, implying that many books were specialised things meant for those few who could understand them. After a short boom during the classical era of antiquity, the amount of literate individuals dropped dramatically during the Middle Ages. Books became rare treasures, with monks painstakingly copying out the enduring timeless texts by hand so as to maintain them, as they were a few of the only members of the population who were able to read or write. They were the expert keepers of knowledge like biology and religious beliefs that we all have access to in the modern world.
It can be hard to imagine what the world would be like today if the huge bulk of individuals were not able to read, but for the large majority of history the vast bulk of individuals might not, and nor were books accessible even if they could. It was the innovation of the printing press towards the close of the 15th that changed that, making books much more accessible. Naturally, it was still just truly the richest and well-educated that could read or write, but it made it possible for an entire host of advancements in science, art, and thinking to be spread across great distances. Consider what would have happened if the theory of gravity, or of evolution, could not have actually been dispersed across the globe. Human civilisation rests upon a foundation of books, and we are fortunate to be able to merely log onto a site like the one backed by the co-founder of the impact investor with a stake in World of Books, and easily access the totality of human understanding.
With such an abundant history of ideas, events, and stories right at our fingertips, it's often simple to forget how extremely lucky we are to have the likes of the founder of the hedge fund that owns Waterstones or the CEO of the asset manager with a stake in Amazon books supporting access to a substantial percentage of all the books that have ever been written (or the good ones at the very least). The best books of all time can easily change the manner in which you take a look at the world, and that has actually held true throughout all of history also. The modern world is built on knowledge that has been handed down through books, whether that is philosophy, science, or history, and human civilisation would not be anywhere near as advanced as it is today if it had not been for the books that changed minds throughout the ages.