Mission of Honor, by David Weber
Weber's long series of books set in the "Honorverse" (NB: link may contain spoilers) is thoroughly enjoyable if you like "military science fiction". That is, if you like mind-cheese with lots of stuff blowing up. Unlike most other authors in this sub-genre, Weber even manages to make his characters believable and sympathetic, to sometimes have realistic conversations and motivations. And the universe he creates is, on the whole, consistent.
The series went through a bad patch a few books back where there was lots of "jaw jaw" and very little of the "war war" that made the series so exciting. But I'm pleased to say that with the previous installment (At All Costs) and this one, he's back on form.
I have three criticisms. The first is that the books will make little sense unless you've read the previous installments. That's fair enough. Authors writing series have to strike a balance between making later works accessible to newcomers and annoying their established customers with repeated material. In a short series, a bit of repetition won't do any harm, but in this one - 12 books so far, with at least two more in the pipeline and quite probably more to come - it would be actively harmful.
The second is related to the first, but is, I think, rather more important. There are several spin-off series, also set in the same universe, which some readers may not have bothered with. Unfortunately one of them, the "Wages of Sin" series, turns out to be of vital importance, and the "Saganami Island" series is also of some relevance to this book and, to a lesser extent, to the previous one. Keeping track not only of a long main series with several parallel interacting plot threads (but at least they evolve alongside each other in a single series) but also of at least one and potentially several other series at the same time is hard. It's worth doing, but hard.
And finally, remember how I said that the universe Weber has created is mostly consistent? The big economic inconsistency is beginning to bite, hard. He knows it - he even has some characters talk about how it makes no sense. He tries to justify it as being a front for a huge conspiracy, but huge conspiracies just don't work. The one he's written involves literally millions of people, at least thousands of whom are scattered all over the place amongst other polities and societies, and they're actually multi-generational sleeper agents. He expects us to believe that the children of sleeper agents will be content to be brought up as normal people (you can't trust young children with such secrets, after all), to form friendships, perhaps fall in love with members of the host society, and, when you inform them of their family's hidden role for them to just accept it. Even if somehow most of them held it together, all it would take would be for a handful to blow the whistle and, given how many there are, this must happen - and yet it doesn't for hundreds of years, not until narrative imperative compels it. I can ignore this, I read lots of sci-fi, much of it in the "bad but entertaining" mould, and so my suspension of disbelief muscle gets a regular workout. But even so, it is irritating.
Those last two niggles, plus the entire series's utter lack of anything approaching literary value means it gets only three stars. I recommend it for those who are already Honorverse fans (not that there's much point in recommending it as you'll all buy it anyway) and I recommend the Honorverse as a whole to all sci-fi fans, but I have to insist that you read the books in order. Specifically, in publication order, so that you get the other series at the right time.