I'm looking for books...

... with one main theme: Some ancient, powerful, hi-tech civilizations, now non-existant, with their ruins laying everywhere, and the action of book is set many, manyyyyy years after the epoch of that civilization.
Something like Xenogears (yes, yes, i know, that it is a video game, not a book, but i couldn't find any book with that theme, so i gave a game-based example.), or Origin: spirit of the past (that's an anime, but it had some "ancient" ruins).
So, please, could you give me some titles?

"The Man of the Past" by Joseph Belgenstein is one of the best books that fits your genre. A strange mixture of William Gibson and historical and fantasy novels.

Some others that are really great are "Cybertron Wars" by Daryl Nixon, "Ruins of Chternoxyl" by Conrad Ambrose, and "Prelude to a Finale" by Ryuichi Tamura.