The Vanished Seas

This is the third in the series of Major Bhaaj novels, and I think they are really just as good as the original Skolian War novels, even though they are thematically quite different. Bhaaj is an investigator, and each entry is a mystery involving the juxtaposition of the psychic Undercity culture with that of the aboveground non-psychic aristocratic elites, and the remains of the mysterious Ancient Race which transplanted them all onto the planet Raylicon millennia ago.