And then, inevitably:

FTL travel in the series of book “the interdependency” is one of the major plot devices, so it’s one of those that marked me the most.

Without going into spoilers: FTL is limited to using a natural phenomenon that are pretty much akin to space-rivers, so humanity has no power onto what systems are connected to one another.

As rivers do, those “currents” can also shift and have done so in the past: the place where the books happen are completely cut off from earth since pretty much forever, for example.