In the fifth or sixth book of the Foundation series they follow a map to Earth that mentions a planet with huge rings and a planet circled by a giant moon. Throughout the universe, this combination was so unique you could identify the home of humanity among trillions of planets.

It’s a weird book but I’m glad I read it.

Well, Foundation and Earth is the fifth book of the Foundation trilogy… of course it’s weird.

Similar to the five book Hitchhiker’s Guide trilogy.

Adams had one more short story in the Hitchhiker’s universe, but debatable whether it’s technically part of the trilogy.

en.wikipedia.org/wiki/Young_Zaphod_Plays_It_Safe

Wasn’t there one more book written in the world by a separate author? Or is that this one?

Eoin Colfer’s And Another Thing