I may not be able to recall most of what I read when asked on the spur of the moment, but much of what I read resurfaces when the occasion arises--in a conversation or when reading another book that references information I've read previously. My subconscious background has been broadened--and maybe my understanding is more complete when an esoteric subject arises.
Even in fiction (especially if a book sends me to research an actual person or event) the information can be relevant in many other instances. Novels that I can't even remember have led me to explore historical events, to reconsider social problems, to question my previous beliefs, to become more empathetic and understanding of certain situations.
I read a lot, and much of what I read is purely for entertainment. But even bad fiction can provide insight. When I read nonfiction, I find myself more critically aware of what I read in fiction. As a result, a novel I've all but forgotten may have influenced my reading in ways beyond conscious awareness, and nonfiction reading can help me appreciate the characters and events in various novels and to judge the accuracy of the history or setting.
I love this article about librarians on horseback.
There are more photos and information in the article. Librarians are, indeed, amazing! This was not an easy job, but these women could certainly be proud of the work they were doing.