I enjoyed the book. However, I have a minor complaint : even if it describes extensively virtual hells, it never mentions what determined if you went to hell or not, and for how long. Even if its a minor plot detail missing, in itself it could have been an interesting topic.

In the case of Surface Detail the characters who were in Hell had chosen to go there - I thought it was reasonably clear that the other souls in Hell there were there because they were "bad" (for some suitable local definition of "bad").

That's the bad part that is bothering me. Did they replay your whole life once you died and gave you some score for each event or decision ? Who established the rules and the scoring ? Would it change with societal change in a given society ? Could you evaluate yourself at any point if your life to see if you were a "good" or "bad" person ? Could you hack the system by implanting false memory ? Or could you wipe out some embarrassing parts? You could write a book on that topic only.

I agree those are interesting questions not directly addressed by Surface Detail.

However, on a related topic the novella A Colder War by Charlie Stross has a particularly creepy ending if the idea of virtual hells bothers you - the idea that an intelligent entity actually enjoys running simulations of minds and exploring the ways they can end:

There is life eternal within the eater of souls. Nobody is ever forgotten or allowed to rest in peace. They populate the simulation spaces of its mind, exploring all the possible alternative endings to their life. There is a fate worse than death, you know.

http://www.infinityplus.co.uk/stories/colderwar.htm

Vernor Vinge hints that transcendent Powers can sometimes do similar things with the minds of lesser entities:

"This innocent's ego might end up smeared across a million death cubes, running a million million simulations of human nature."

The virtual hells computers were a sort of AWS for civilizations that became space faring and had religions that instituted them. But did not want to run the hardware themselves, because it was too icky. So a whole collection of hells ran on those computers for different societies and different reasons.