I would just let them pile up until I could build a book fort.
1. Women and Children's Shelter.
2. Men or Women Homeless shelter.
3. Teen Homeless Shelter.
4. Local schools
5. Old folk center.
6. Jail.
7. Fire Stations.
8. Halfway Houses
9. Literacy Read Program Centers.
10. Low income neighborhoods libraries.
I keep all my favourites, the ones I buy in hardcover . I donate the rest to goodwill with about 10 garbage bags of clothes at least once a year ... I buy too many clothes :/ I have to get a handle on that then ... Stat.
I have stacks of books in my office. Every year, I swap a stack of mine for a stack of my daughters.
I push delete!
When I get too big a pile on the floor, I usually take them to the Library. Looking at a pretty good sized pile right now !
I donate them to Goodwill. I have been thinking about putting a "Little Free Library" though. In case you haven't heard about those, it is a small cabinet you put outside where people can take book. I just have to check with my HOA and the city. My property includes a water conservation area with a protected buffer zone, which limits a lot of what I can do.
Most of the books that I read are from the library, so I'll return them. For the ones that I own, I usually keep them, and lend them to friends if they want to read it, or keep it and reread it several times (Harry Potter).
I go through my books pretty regularly. The ones I don't save go to Goodwill or the library. The library will accept donations and will sell them.
I keep the ones I really enjoyed. I enjoy way too many. Many I get rid thru a book swap wedsite. Others go to a local Hospice charity.