Books with mysterious ruins, and forgotten technologies

Hi everyone!

After reading the Gideon the ninth, I wanted to read some other stories with similar settings, but I couldn’t really find anything yet.

What I really loved in that was the searching for the forgotten technologies, the mystery around the ruins, and the creatures that were really creepy and gave a specific vibe to the novel. I’m looking for something similar to this storyline.

After this I’ve read The Will of the many by James Islington, which also had these features a bit, but I guess we’ll see more about that in the upcoming books.

Does anyone know more books with forgotten technologies, mysterious monsters, and ruins abandoned by mysterious people?

by Xiaoge_