Some of them. I couldn't possibly keep them all. I would be buried alive! I get a lot of books from the library, and read some electronically. Of those I actually own I keep only those I plan to read again or am particularly sentimental about because they were a gift or remind me of a special time or place. That's still quite a few.
I generally do not keep fiction books as I work in an op shop and can get them easily.
Also I collect old children's books (or used to) so I have two big book shelves full of delightful books, so have no need to keep a novel.
I keep many of Adult Fiction books I have read,but only those I want to enjoy again at a later date.
I always keep my gorgeous reference books as that is why I got those in the first place.And as for my old and antique books? Well,it's probably better not to go there!!! I have a very extensive collection of illustrated children's books from the late 1890's through to the 1940's which I will NEVER part with! I enjoy the collecting,the research,and the actual books themselves.I do read these delightful old treasures and I always go back to read them over again,and again! There was an innocence and respect,as well as a sense of absolute use of imagination, inherent in all of these old stories as well as a wonderfully whimsical type of humour which made them so super for parents to read aloud to their children in those pre technology,and even pre-TV days!! They suited both boys and girls,and I have enjoyed many a chuckle at such a huge number of stories and books which would benefit from a new edition being released nowadays!!
My answer is the same Jennifer and jonaj's combined. I have kept a set of my dear father's westerns as they were his favourites and I used to read them too. The shame is they are not on Kindle :(( I love my Kindle. Did I say I LOVE my Kindle . . ?
Most of the books I read these days are from the library. I rarely buy fiction and if I do would only keep a book if I planned to reread it. I have a few non fiction books which I keep as reference books. I used to buy and keep lots of books when I was younger.
My husband and I both give our read books to an op. shop nearby. And, I think the op. shop charge too much for them, even though most are still on book shop shelves when we donate them to the op. shop.
Some op. shops need to reduce their prices to free up shelf space. No money made out of stuff sitting on the shelves til they turn yellow.
I have a few big book cases just full of books. I am presently looking at decluttering. I want to sell my old uni books and also get rid of some of my novels that I will never read again and that I'm not sentimental about. Free up some room for new abundance to come into my life.