As usual for Mr Chalkers work there is a theme of people changing form into various other types of body. This is probably the best implemented of his stuff in that the reasons why people hace to change is integral to the plot. Essentially the universe is an artifical construct controlled by a planet-sized computer far away. This computer is also a world where various races have been created and given an environment to live in to see if these prototypes could survive in the wider universe. Each environment is a hexagon (Which makes maps very easy.) and there are 1560 of them. Quite a large degree of creative freedom there.
The worlds creators are long gone, and the story tells more or less the tale of the repairman who has to reset the computer when it becomes damaged.
Fairly straightforward SF for the most part. What intrigues me is the lead character, Nathan Brazil. He goes through various permutations from claiming he is God, to being one of the creator race left behind, to being trapped into fulfilling the role by a previous incumbent who wanted to die, to being a construct left behind to reset the machine if necessary. You're always kept guessing as to which he really is. But at he same time he is a very human character capable of ruthlessness, compassion and boredom.
It asks some questions I find quite intereseting along the lines of: If god was one of us what would he be like? Which is switched to: If one of us had god-like powers what would they be like? In the story Brazil just wants to be left alone for the most part, and resents being forced to take responsibility for effectively every living thing.
I suppose its an optimistic take on the topic because there is always a way to start again, and when he is possessed of ultimate power over the universe he can't wait to put it down again. At first he just wants to pass the responsibility to someone else so he can die, but in time he finds he can't do that to another person, and finishes up going back to live as a normal man out in the universe again.
My only real critism of this autors work in general is a slight streak of mysoginism in that women who are transformed into men seem happy with the alteration, whilst any men who the reverse occurs to resent this violation of themselves...
Nevertheless I enjoyed reading it all again.