I am a bit suspicious of this book, because I cannot pin down precisely why I enjoyed it so much.In general, I do not enjoy military fiction, but this one took me from "stayed up late" to "stayed up early."It's a sequel to The Myriad, a book which gives you a very decent military SF story, and then in the very last chapter gives the reader a surprise kick to the balls.(I am not equiped with balls, so my surprise was extreme.)I think I would recommend it if you enjoyed David Feintuch's early Midshipman books, before they became repetitive and whiny.I cannot say if fans of Military SF would like it, though, because the charms of that genre are opaque to me.
I think you could read Book 2 without having read book one, but you will be depriving yourself of certain subtle enjoyments (and a kick in the nuts).Everything which is right about this first one is right about this one, from my review of that one: The world and its characters more original than I expect from the genre, and the physics are almost a character on their own. It's action packed, and neither the military action nor the periods between ever seem to drag.
One thing that annoyed me: much of the military action was between the Roman empire, which never fell, merely went underground for two millennia (is this awesome y/y?), and the US of A.Consequently, it's a very western clash of civilizations.In the USA military, I recognized patronymics from all over the world, but the ranking officers seemed to have suspiciously Western-European surnames.
On reasons why I enjoyed it, I think part of it is that the characterization is deeper than is the standard in some military SF, such that one wanted to know what happened to the characters more than the outcome of the battle.
Another caveat: at one point, the US military sends our heroes to investigate a Roman project with a suggestive code name.My respect for military intelligence is not vast, but I do think they have generally proved themselves capable of coming up with codenames that cannot be deciphered by an idiot with a thesaurus.