it doesn't have to be deep or reflective or sophisticated or anything.. (of course it can be as well lmao) just something you think is so good that you want to tell everyone you meet to read it... for example i think that in the miso soup by ryu murakami is a book that i will always recommend to anyone. it's FREAKY!!! but i always think about it and the way it created an atmosphere of discomfort even when nothing was happening was incredible and unlike anything else i'd read