We follow the lives of a physicist, his wife and their friends for several years as the lab struggles to produce results with an experimental instrument, one that may reveal the nature of causality. It's not time travel. Don't call it that.

The central metaphor -- software version control -- could have been better explained in the book (it's a very brief bit of exposition, don't worry.) Nearly everything else about this novel is excellent. I think the version control concept could have been even more powerfully explored by digging a bit deeper on real versioning ideas ... but maybe that's too much to squeeze in.