I try to add new ones that have probably not been mentioned:
The Gospel According to Jesus Christ by José Saramago (Portuguese Literature Nobel Laureate). Brings a brilliant insight of the events surrounding the establishment of Christianity by Jesus. It is not precisely something I would recommend to absolutely everyone, but certainly everyone that is/was christian.
One Hundred Years of Solitude by García Márquez or any of his novels or collections of short stories. I do not think any of García Márquez's books have taught me extremely deep life lessons, but I still think everyone should read some of his books just to experience his amazing storytelling. Additionally, I think his books can be useful to more deeply understand Latin American culture, so García Márquez is a must read for anyone interested in Latin America.
Don Quixote by Miguel de Cervantes. Don Quixote's ridiculous lifestyle makes this novel a really fun read. Nevertheless, I think its deepest value comes from the theme of fiction versus reality that the novel discusses. I think that all the content that has been created using this theme makes Don Quixote a valuable read.
