This is one of the few manga-based-on-a-light-novel which actually inspired me to read the light novel. When I first read this, I read it through, and then I immediately turned around and read it through a second time, and then I immediately read the light novel through, and then immediately read the manga through a third time. Some point after that, I read it through a fourth time. And for the purposes of writing this review, I've now read it through a fifth time. So I can confidently say that I generally enjoy this manga.
So why did I give the story an 8/10? Well, there are definite lulls in the story (for example, the entirety of the Dark Prison Realms storyline) and the story goes through some cycles which can become a mite repetitive over the course of a long series. More than the story itself, I think the characters hook me with this manga. Nie Li is quite possibly my favorite manga character of all time. He's honest about his feelings. He's intelligent and cunning. He's powerful, yet playful, enjoying taunting and teasing people. The absolute best aspect of the story, and what makes it worth reading again and again, is Nie Li's wooing of Ye Ziyun. This of course includes his interactions with her relatives--her father, Ye Zhong, in particular.
As for the basic premise of the story, Nie Li died while fighting the Sage Emperor after traveling the world beyond Glory City and gathering extensive knowledge of various things, including alchemy and cultivation techniques. Upon his death, his spirit goes back in time to when he was thirteen years old. He knows that Glory City will be overrun by demon beasts in several years, so he uses his knowledge from his previous life to increase his (and his friends') cultivation speed and political power so that he can fight back against the demon beast horde when it arrives. He also intends to get revenge on the Sacred Family because they betrayed Glory City in the previous timeline. And in the long run, he wants to build up enough strength to be able to fight the Sage Emperor and actually have a chance at winning this time. Nie Li often fights people several levels stronger than him (after all, having the weak overcoming the strong is much more palatable than having the strong stomping on the weak).
He travels to different realms, makes allies, gains treasures and trump cards he can use in battle, and generally increases his military power. Along the way, he defeats some enemies and begins to focus on new, stronger enemies. This cycle of finding new enemies and gaining strength can continue indefinitely, but is kept fresh for the most part because how he's getting stronger is switched up from story to story. Though, again, all that probably wouldn't be worth reading if this story didn't have the wooing aspect to it. That's what makes the story.
[Reviewed at chapter 247]