Plus a lot of them are fun as heck to read, page turners, not at all difficult, e.g. Pride and Prejudice or The Hunchback of Notre Dame, The Count of Monte Cristo and so many others.
I'm currently reading Sei Shounagon's The Pillow Book. The author was a woman in the Heian court in Kyoto about 1000 AD, attendant to the Empress. By tradition it is a collection of her dairy entries, letters, poetry drafts and other personal papers, not intended for distribution, at least in the form we received them. It's unclear if the whole work is even a single author's.
I went in expecting not to understand parts of it. And that has been true. But I also didn't expect to laugh quite so much! At one point, she has a list of grievances over the aggravations of daily living and bad etiquette. The more irrelevant and trifling, the more hyperbolic she is. At one point I fell right right into it and I was in the scene. I have lived those very moments. And I feel her same bizarre gulf between the urge to be polite outside, and the frustration with the people being impolite on the inside. I am pretty sure I have felt some shadow of what she felt in Kyoto some thousand years ago. It is both jarring and pleasing to have that momentary connection to someone who is about as alien to me, as anyone who has left a written work could possibly be.
But I’ve read four Jane Austen novels (three for credit, one for a failed shot at a Women’s Studies major) and not enjoyed a moment of the experience. Intellectually, I get the quality of the work, but it wasn’t entertaining. It wasn’t pleasant, and life is just way too short for that. Books, even technical ones, get about three chapters to make their case now, if I’m not voluntarily choosing to read it after that, I’m moving on.
However, I do know the feeling you describe: sometimes, it just doesn‘t „click“. And in that case, I will eventually move on to the next book, and try not to feel guilty about it ;-) (I started „Paradise Lost“ twice. I love the absolutely epic poetry and vivid imagination, but I still ended up getting stuck both times...)
So many are free on librivox (or from a library): https://librivox.org/
PS no audiobook version could redeen Paradise Lost for me either, it was my peast favorite reading in high school. To paraphrase, better to be ignorant in hell than well read in heaven if you have to trudge through Milton to get there.
https://en.m.wikipedia.org/wiki/History_of_the_Peloponnesian...
Another reason is that lately, reality is both more fantastical and absurd than fiction. Contemporary books come off a bit pedestrian.