I read the first volume. I haven't quite gotten to the second yet.
It was okay. I haven't read Rebellion, either, and I intend on going to that soon as well.
Rebellion is a direct sequel to Empire, similar to how Republic led into Dark Times. So you should appreciate the transition.
The quality of Empire grows as the series progresses, in my opinion, barring the first story arc. Having read the whole series, Empire is certainly not as good as Republic, but it is still very good. So stick with it. You should enjoy at least some of it.