This is gonna be a hard one to review without spoiling because I was mostly checked out on this story until around the 85% mark, where something happened that finally made me sit forward with attention. But lets get the early stuff out of the way first.

In theory I don't need my science fiction to have really elaborate worldbuilding and spaceships and aliens and whatnot. I'll concede that it is possible to tell a compelling story in a contemporary setting that has just one or two elements that give it that ~sci-fi~ spin on it, which is what we get here and we figure that out pretty early on. But when you start playing around with infinities and infinitesimally small chances for certain events to happen, it's gonna feel cheap and unearned when those best-case scenarios... happen.

We have in Jason Dessen what I found to be a fundamentally unlikable protagonist, and I don't know that the author intended for him to come off that way. He's a chauvinist who has an almost possessive relationship towards his wife that goes beyond mere affection that made me uncomfortable, and for all of his academic accolades (of which we're reminded of frequently), he makes frustrating decisions and just kind of fails upwards and into the right trajectory because why wouldn't he?

This story had the potential for some truly Shakespearean levels of tragedy and copped out for an ambiguous but mostly feel-good ending that felt undeserved. Call me a psychopath, but I just feel that these characters did not suffer enough for my enjoyment to get the wrap-up that they did (holy shit, that sounds insane now that I'm reading that). Anyway, if you want to read something else that also tackles themes of regret and "what ifs", read Militia House by John Milas.