I love idea stories. Idea stories are what hooked me on SF in the first place. Divided by Infinity is almost a pure idea story, though it has some good characters wrapped around it. It was nominated for a Hugo for best novelette in 1999.
The idea is a variation on the "many worlds" hypothesis of physics--that at each point where things could have happened differently, they DID happen differently, in some branched reality. The argument is that, once we come together as conscious beings, our consciousness maintains contact with all these alternate realities. And it keeps going on, as long as there is some reality, no matter how weird, in which we could go on.
Now, there are a lot of holes and gaps in making the leap to having a consciousness that spans realities. When would we, as individuals, start? How does our sense of being in one place transition across possibilities? The "many worlds" theory itself runs into a lot of trouble as an explanation for reality. We end up imagining a cosmos so big, that everything that could possibly happen has happened, an infinite number of times. That has no explanatory power at all.
Wilson doesn't fight this implausibility, he just works it in, which makes the story very interesting and worthwhile to read. Am giving it four stars, go experience it for some mental stimulation.