Books (largely) aren't written for memorisation these days, with possible exceptions of some poetry, or children's books.

Classic oral literary traditions are based on rhyme, meter, repetition, simile, metaphor, and references to cultural touchstones and themes, for the most part, all of which strongly assist with memorisation. These are not only necessary for a literature which isn't written down and instead is passed on through generations orally, but also quite likely represents a survivorship bias in that works which didn't exhibit these patterns didn't survive. And of course the versions we know are the end of a long pipeline of transmission (or the world's largest and oldest game of telephone), captured in writing and then passed on to us as (among) the first written traditions.

I've committed a few poems and homilies to memory, one example for nearly thirty years now. I do refresh that recollection from time to time (and realised I was dropping a stanza consistently). It's an interesting counterexample.

Then again, I turned up a piece earlier today I'd written myself about eight years ago and had all but no recollection of.

The point was that with Plato (but also ~2,000 years before his time, with the Sumerians, who probably invented writing) we were already discovering that we don't have to bring the exterior into an inside which we call "self", memory, we can actually leverage stigmergically [1] the environment to enhance and extend the "self", i.e. by writing, leaving a mark; the Greek word grapho γράφω [2] meaning literally to carve.

Not sure if LLMs will enhance our current "self" by themselves, but once we get a chip or two inside our brains, once we start controlling the cells to regenerate or grow specific limbs [3], we will surely consider our present "selves" as tiny as we consider the "self" of one of our cousins, the chimpanzee, in a zoo today. The journey and expansion of the "self" is merely starting.

[1] "the trace left in the environment by an individual action stimulates the performance of a succeeding action by the same or different agent", https://en.wikipedia.org/wiki/Stigmergy

[2] https://en.wiktionary.org/wiki/%CE%B3%CF%81%CE%AC%CF%86%CF%8...

[2] "HCN2 Rescues brain defects by enforcing endogenous voltage pre-patterns", https://www.nature.com/articles/s41467-018-03334-5

Isn't it a thing of honor in the Islamic world to be Hafez (?), someone who has memorized the Quran?

Of course I have no way to check whether it's done correctly, but from what I hear a lot of people have done this.

We just use our brains differently now, mostly to find ways that support our default positions, that leave our minds unchallenged and certain.

If we wrote entire books in song, they could probably be memorized. Shakespeare attempted some of that work.