Five star books you have forgotten

I've read a lot of books, and I have forgotten a lot of books. Most of the books I've forgotten were three star books, fun, but not very memorable. There are, however some books that many consider five star reads that I have read, enjoyed, and forgotten.

I am embarrassed to admit that I don't recall much about A Hitchhiker's Guide to the Galaxy. I do recall enjoying it but honestly, the only thing I remember is that the Earth is about to be destroyed to make room for an intergalactic high way and that, for some reason, you're always supposed to have a towel?

I skipped almost an entire day of class in college to keep reading Wally Lamb's She's Come Undone, yet plot wise, I remember nothing about that book.

I watched the BBC dramatization of Zadie Smith's White Teeth and liked it so much I immediately bought and read the book. I remember being really impressed with the writing, especially since we were so close in age (and I was so young back then). Now, all I remember is I think someone is a Jehovah's Witness?

They were all books that I really enjoyed but, for whatever reason, they just never stuck. In fairness, these books were read like twenty years ago. Then again, I read Dead Until Dark (the first Sookie Stackhouse book) around the same time and I definitely still remember that book well so I'm not sure why some books stick and some books don't.

Are there any top tier, five star books that you have read but forgotten?