Aldiss' future reminds me of one of the early 1980s classic sci-fi B-movies, Cherry 2000. The world is overcrowded, 75% of it is starving, and housing is expanded vertically to accommodate everyone. In the midst of it all, governmental population control has allowed a crowded city to become a Utopia. We might balk at this idea, but China exerts this power in the form of financial compensation and penalization (as of a few years ago when I last read about it).
 
 

In Aldiss' story, apartments are the primary form of housing, and nobody would prefer one with actual windows because the crowded city is all one can see. Instead, video screens provide a view of whichever world a person wants to see. Holograms can even turn the entrance to an apartment into a country garden with a clear sky overhead.   With all of this great technology, the disparity between the rich and poor seems fairly clear. The rich can live in Aldiss' city, have these wonderful luxuries, and eat to their hearts content. The poor are among the 75% starving.