After 300 left quite an impression on me few years ago, I was looking forward to the followup.
Basically (well spoilers ahead) it's about the side-story of the whole 300 story. The story of the other side of Greek while the brave Spartans battled Xerxes.
Eva Green's performance stood out for me.
Lesson of the movie : never mess with the ladies!
All in all, 7/10 for me.