Brust and White start with an interesting premise: what if there was a secret organization working behind the scenes of history to make things better--just a little better. They argue about how, precisely, to do that, but when they do, it involves "meddling" with other people, subtly influencing them to do or not do something that changes the world incrementally. 
 These "Incrementalists" live human lives, except that when they die they can be reincarnated into the bodies of someone else. When that happens, either the old personality reasserts itself and the body's personality gets folded into the underlying self as memories and perhaps a few traits that peek out. 
 At the heart of our story is Phil, who has been the longest consistent personality in the group, and his love affair with another Incrememntalist, Celeste, over the past 400 years. After Celeste's apparent suicide, however, well, things change. 
 At the end of the day, though the premise lends itself to watching these characters try to change the world, instead the novel focuses on the relationships between these Incrementalists and the ways that Celeste has changed the rules by meddling not with regular human beings but with the Incrementalists themselves. 
 The book was a fun read that also raised some interesting ideas about agency and free will as well as relationships and how they influence us.