Although many people use eBooks these days, paper books, I personally doubt, are never going out of style. However, have you become a hoarder of books? Don't throw them away! There are many options.
Much of this list pertains to the United States. However other countries may also learn.
Little Free Library
I have always wanted to make one of these.

Pixabay
Salvation ArmyI go there once or twice a year. They have a huge book selection. I am sure they would have a nice place for yours. I once wanted a book online that cost over $40.00. I found the book at Salvation Army for less than $5.00!
GoodWillThey accept your books and sell for an amount anyone may afford.
Local LibraryIf not for their shelves, the local library often sells such donated books to raise money.
Gift basketsWhether to create gift baskets for personal gift giving or to sell, a really cute option.
Yard saleMake some extra money!

Pixabay
Book swap
Just like a clothing swap, have a book swap.
Give to a good homeDo you know someone that is always reading books? Give them your books!
Pay it forward.
Are some of these options new to you?
If not, what are you waiting for?
Consider it a part of Spring cleaning.
If new to you, consider what would be good for you.
I hope this list has helped.