thrift stores as a lot of libraries don't want them anymore. Little free libraries too.

leave them in a box outside the library. put some in the little free libraries around town (there is a map of them on littlefreelibraries.com)

Where is the best place near Bethesda to donate or sell used books? I am aware of the used book sales put on by local high schools but I don't want to wait for next school year. Thanks!