One of my main criteria when rating a book - and, when skillfully done, one aspect of the writer's art that can just leave me in awe - is the author's ability to bring the reader into an unfamiliar culture with a minimum of pedantry or obvious explication. Given that the culture of this book is one where the inhabitants communicate by shifting patterns and colors (like squids), scents, and other chemical signatures, Thomson's world-building ranks right up there with Frank Herbert's, IMO.