Second in the Honor Harrington series by David Weber...
This is going to be quick and short since it's Honor and Weber and my love for both has already been established.
This is the one where Honor goes to Grayson for the first time, we meet the Mayhews, and there's the whole confrontation with Masada.
The thing that really struck me this time around was the religious extremism. And the complete obliviousness of certain political types to it. That logic just isn't something that will work to combat that level of conviction.
I'm always amazed by authors that can get me completely emotionally involved in a story, especially when it's one I've read before.