So. Jack Vance's The Face , the fourth of the Demon Princes books. The formula for this series hasn't really changed, and this one follows it pretty closely; oddly enough, I'm not yet getting sick of the formula, no matter how straightforward and obvious it makes the plots.
I expect the main reason for that is Vance's world-building, which is here on fine display again. The Oikumene (for so Vance's interstellar civilization is named) is a setting that allows for an enormous variety of worlds and cultures, and Vance takes full advantage of that allowance. All of his societies are distinctive, unique, memorable, and slightly odd. Even when you know what's going to happen in broad outline, it's worth reading for the details.
Now, onto the fifth and final volume.