Back in early 1990s, Ray Aldridge published a trilogy of novels that reminded me of Jack Vance’s Demon Princes series. In the first book, The Pharaoh Contract, Aldridge’s hero, Ruiz Aw, signs a contract with the Art League to discover who is poaching on their slaves on the primative planet of Pharaoh. Ruiz Aw is a skilled agent, but even he is almost killed before this book ends. Slavery is common in the galaxy and various groups compete for the profits such a dark business produces. Like many Jack Vance novels, The Pharaoh Contract features bizarre human societies and amoral violence in a decadent Galactic civilization. I can also recommend the other two books in this series: The Emperor of Everything and The Orpheus Machine.