For me personally, I think a good book is one I DON'T want to read again.
Not because it was bad, but because it was so good the first time, I don't need to read it again. It's there in my head.
For example, the Warrior Cats series by Erin Hunter.
When I was in high school, I LOVED this series so much I bought every book. To me it was unique, creative and emotional, despite it not having any relatable human characters. Just cats. Sure, might be just my bias because I'm a crazy cat lady myself, but I got so immersed in those books. I loved the lore, all the characters that I became emotionally invested in or devastated by certain plots/events. And for exactly that I reason, I would probably never re-read it. Why? because I already experienced it, I won't be able to fully experience it again. I don't want to go through all the frustrating parts, the depressing parts all over again only to know how it ends.
Of course, it all really depends. There might be some stories you revisit after a loooong time because of nostalgia.
Warrior cats might get a brief revisit from me, who knows.
Tl;dr: Books that are memorable af that hit hard after many years.

Eldoria summed up most of what I'm thinking in a way my autistic brain cannot.