Books that left you silent at the end?

I saw a post on here a few weeks ago with a similar title I think but I lost the post. I want a thriller or something that leaves you saying wtf, speechless or just left you thinking for weeks. I saw someone recommend I who have never known men and took the recommendation but really didn’t get that feeling from it and thought it was overhyped. Any recommendations on something that will just leave me starring at the wall?