In a sense, Ecce and Old Earth continues the trend of its predecessor, Araminta Station, in that it's more directly a detective story than most Vance books. Its protagonist, Glawen Clattuc, is, after all, a policeman, and the book traces his search in parallel with that of his love interest, Wayness Tamm. But where Araminta Station focused mostly on the planet Cadwal, here we're treated to Vance's gift for creating weird and wonderful landscapes as the two protagonists pursue their separate searches. Unusually for Vance's SF, we spend a fair amount of time on Earth itself, and while some of it is changed past recognition, it's fun to see places such as Trieste through a Vancian eye.
The result of all this is a book that's entertaining and colorful, and the best in the Cadwal Chronicles series. While the series as a whole doesn't match Vance's best, it's still good, and this book is very good.