Hands down the best military SciFi I've ever read. This book was the first entry into what has become David Weber's Honorverse. It now encompasses dozens of novels, following both the titular Honor Harrington, a Commander in the Royal Manticoran Navy. The next series follows her through multiple wars to the rank of Fleet Admiral. And not a single one of them is a dud.

The first few books are a bit "Hero Captain/Hero Ship", but not too much, and it gets better later on. Weber later also veers into intergalactic politics, but I wouldn't worry too much: I think what he does show of politics will be palatable to anyone outside the outer extremes of our current political landscape.

The one slight downside of the series as a whole: Towards the end, Weber slowly reveals a massive, Galaxy-spanning conspiracy. And I just hate conspiracies in fiction, but especially ones so mind-bogglingly large as the one Weber has constructed. It's not the kind of "nothing was actually as it seemed" stuff, but it was large enough to make it utterly unbelievable to me. But even the books which contain it still are good enough otherwise for me to slog through.

Also, extra fun is to be had if you're even slightly versed in the Napoleonic Wars.