Arc II, which stretches from the latter half of volume 2, to about halfway of volume III, was difficult for me to read. The change in tone is very drastic. The arc is dark and gutwrenching. It's very well written, and it's good context to Xie Lian's character and the way things work in this universe. But I wished it was a bit faster paced. Personally, I prefer the arcs centering HuaLian's romance, so it was hard for me to read that arc. I hope future volumes don't have such long flashback arcs.
The rest of the book is utter perfection, as always! MXTX is a fantastic writer.