I found this book at least as enjoyable as the first one. It is true that it takes a good chunk of the book before any real action is taking place but the parts of the story that leads up to that point is still quite enjoyable. I generally do not like sequels which more or less takes the focus away from the main character. For major parts of Citadel this is done but it works reasonably well.
The book deals a lot with the science and logistics of building the massive battle stations, of which Troy is the first, and though, sometimes, this can be quite boring in this book it is fun read. You get a glimpse of the alien politics behind the scenes as well. To be honest, I could have been without those parts.
However once the action starts it is literally “Damned the torpedoes, full speed ahead”. I’ve already started to read the third one in the series.