Afraid I had to give up on this one. I quite enjoyed the first fifty pages or so with the initial adventures through the city in the mountains - as usual Aldiss is fantastic at creating an unsettling world.
Since the 'contemporary' part of the story began though, it has been about as interesting as a telephone directory. All the characters are interchangeable and they have the most stupid names and, despite the protracted timeline as we follow the seasonal change, very little happens apart from the odd fight or flounce. The only interesting part of the plot, and the only SF aspect in this mundane fantasy book, is the orbiting observation craft from Earth which makes 3 short appearances in 500 pages.