I don't know whether any of these would suit you, but here are a few suggestions. Some villages have set up little libraries in telephone boxes for the community. However, that might not be an option for you if you don't live in a small village community, just a suggestion. I've seen some set up a stall outside their home with a "please help yourself" Not in the pouring rain of course. Even in pubs too!
There are several on line sites where books can be sold. I've not used those because I'd rather donate. I once bought more books than I do now and some of those I donated to my library, they were best sellers in good condition. I've also given some to friends.
Local hospitals would also be a good place to donate. We even have a "help yourself book shelf" in the shopping mall in my local town, situated near the loos.
We had a charity shop in the town where I used to live, who dedicated one of their shop to books only. The books were properly arranged by category. It was well liked, throughout the town, almost rivalled Waterstones.
I hope you find a trouble free solution.