This manga is definitely in a class of its own. I like going back to it once in a while because the plotwork is very intrincate, the heroine is a complex character who grows and the political intrigue, the complexity of the rest of the cast, and the action are all top notch. It's one of the better historical/sci fi genres out there. I really found myself pulled into the plot and the characters. It's creative and emotionally wrenching at times, although romance does take a backseat. One of the best aspects of the manga is the lush characterization of secondary characters like Asagi. It is not only the main character that grows but the entire cast. It is also full of symbolism, archetypes etc.
That being said, this is for older audiences that don't mind a lack of the tradition lovey dovey type of romance or gradual buildups for relationships. I do feel that although the rest of the manga is excellent, the romantic aspect is a tad unrealistic if you're cynical like me, but the ending is climatic and gives off the tone and atmosphere that it was striving to achieve.
On another note, the artwork is good but not clean cut. I, myself, prefer crisp lines and shapes so the artwork here isn't my ideal cup of tea.
Overall though, this is definitely a series everyone should check out. It has its flaws, as with everything, but in terms of all the mangas I've read, this definitely touches pretty close to perfection.