At a used book sale more than three decades ago I bought a complete set of the works of Mark Twain. The books were old, but in good condition and very cheap. I have never read any of them, although I have read a few books by Twain since then.
I soon discovered that a red residue from the covers of these books stains one's fingers, clothing and anything else the books touch. Also, most of the pages in these Twain volumes were still uncut, indicating that the previous owner or owners never read the books either.
At one time book publishers routinely left pages uncut, leaving it up to the first reader to do the cutting. Some readers found this to be one of the pleasures of reading. When you are the one to cut open the pages, you know with certainty you are the first to read that particular book. I believe some collectors are willing to pay more for old books with uncut pages.
On can still find books with pages that have ragged edges, as if someone had just cut them. Doubleday books used to be like this, and maybe they still are. I've always liked the look and feel of ragged book pages, as opposed to the smooth edges one usually finds.
Reading Liza Picard's Victorian London recently, I was interested to learn that newspapers sold in England at that time had uncut pages. Newspaper readers carried knives, with which they would cut open the pages of their newspaper as they read.