Every once in a while someone comes up with an idea and you slap your forehead because it feels obvious in retrospect. Lockstep is one of those.
Traditionally, in SF, if FTL travel is impossible, but stasis is possible, easy, and cheap, you get interstellar travel that's a one-way trip. Lockstep adds "why not hibernate EVERYONE so they wait for travellers?".
And once you have that idea, you get "fake FTL". But that also brings up the question of how long is it a good idea to hibernate. And once there is a large network of worlds hibernating in lockstep, does it make economic sense to hibernate less than them? Or more? How about resource accumulation on hibernation? How about enforcing lockstep? And so on, and this book explores a lot of that.
So, the world building is awesome, plus it's original! The plot itself is sort of a throwaway.