what we get from reading a book?

To this point, I've read more than 30 books. At first i had that habit of highlighting sentences which I can later come and view, but I slowly learned that won't be much useful. I do still mark or highlight point that I think should be thought critically or are imp for me.

But still I rarely open old books and check those. Because there are lots of them by this point. And when I read book, it feels great, and whatever I read, it sticks in me for a few moment after I close the book. But still when I try to remember what I just read a few hours later, it's hard for me to remember key things.

So this raises a question about what am I reading? if I can't stick smth into my head, why even read it? why even pour that time and energy to know those informations if I can't remember ~99% of it a year later?

First of all, I realized that this differs book by book. Some book, even though I tend to not remember a lot of its exact things as said, it still changes my world view a lot. There are lots of books like this for me, actually almost all books are like this for me. When I force myself and try to remember few key things from a particular book i've read, it's super hard, and I won't be able to do that correcty a lot. I do will remember few key things, but that's more like a context and story rather than actual few 'key points'. But even though I tend to remember super less, every book i've read to this point have affected my world view and how think about things or perceive world in general. And some did a lot, and others not much.

So when I question, why should I read even though I tend to remember super less of what I've read to this point, what should the answer be? Probably reading is just a thinking exercise with a few new ways to look at the world? it does seem so. So I don't need to remember things from book I read? Idk. I do remember things, it's not that I completely forget everything. Like whenever a context arises or something happens that relates to what I read in books in past, that comes up in automatically, so I guess there's that context still that is sitting there, and that gets only remembered when something related happens.

But whatever, probably we'll be reading a lots of books throughout our life, and probably 'remembering key points from what we read' is less important than that book affecting us or changing our world view or just making us think more critically about things. At the end it should change or effect, even if it's slight, the way we think or reason about things and perceive the world. Because within a few decades we won't be here.