What do you do with books you never want to read again?

Let them pile up on the floor.

Over many decades I have developed something of a system.

I try to buy used books whenever possible. I generally avoid copies that are marked up or broken-backed, unless I'm certain I am willing to eat the entire cost in order to have that copy available to read. Periodically I take my no-longer-wanted books down to Powell's City of Books to sell, which is a great resource, but it is mere luck that it is located within an easy distance from my house. I sell whatever they are willing to take.

There are always a certain number of books Powell's won't take, just because they don't need that particular title on the day I'm selling. If I know they are likely to accept it at another later attempt, I save it and try again later.

This leaves me with a residue of unwanted books that are still readable, but probably not sellable to Powell's or other commercial used bookshops. These books I donate to the local Friends of the Library group, who run a charity shop within walking distance of my house. In the rare cases where a book has become a piece of junk while in my possession, I toss it in the trash.

I know this sounds rather elaborate, but it is second nature by now.

Charity shops.

But I don't know what to do with the pornographic stuff Oxfam won't want and comics which aren't obviously adult from the outside and could get someone into trouble if they sold it to a youngster. Maybe I could put notes on the covers.

Can't be arsed selling stuff online but I might need to eventually. Maybe Bondage Obsession 1-2 will go for good money.
I bought them because I like the comic artist Tom Sutton aka Dementia. I've seen negative reviews of his books because people were looking for books about Buffy The Vampire Slayer and the condition of dementia and were horrified to see his cover art then gave them one star "this isn't Buffy The Vampire Slayer, this is filth!".

I like money but I'm not really comfortable charging much more than twice the price such an item would cost if it were new. Don't want to feel like I'm ripping off someone.

i just assume that the problem is me, and i will be wanting or needing to read the book some other time within the 40 years that remain to me