Agency

Note: I very much recommend reading The Peripheral before this novel, to get full context on the worldbuilding and characters' backgrounds.

The novels in this series hinge on a magic server that, in a post-apocalyptic 2136 London, provides virtual access to the past (as far back as 2015, at the very most) through electronic avatars. Once accessed, however, any particular past becomes a "stub" which branches off in a different direction from the London future, since that contact never occurred in the 2136 timeline. People in the post-apocalyptic timeline either engage in this sort of meddling as a hobby, or as would-be saviors trying prevent those alternate universes from ending up with the same dire future (or worse).

For readers who are able to suspend disbelief in the time-travel handwavery, the novels are very readable and enjoyable. However, the fact that there are unlimited universes which can be manipulated for different results really lessens the emotional stakes of the novel. There are interesting variations on tech and AI. And the author has certainly set himself up for unlimited sequels using the parallel universe scenario he's created.