what is the one sad thing about a book that can make you cry?

okay so lately i have realized that crying while watching a movie is very normal and easy because you SEE the person crying or going thru something so most people reflect the emotions back, i feel it's easy cause it is a visual representation on the other hand books need to more intense and impactful to be SAD. ik its about the way you write situations or emotions or use of correct words but still all those things would only matter if one has a v EMOTIONAL incident to attach it with. So, what's the one SAD thing yk incident with someone, a sad state/situation or anything that would make you cry or at least feel thigs?