This manga takes me back. I actually saw Season 1 of the anime, which is the best out of the 3, before reading the manga. Yui Arc was my favorite, by the way.
Once the conquests ended, the story started to get pretty dull. The main reason I stuck around because I wanted to see who Keima ends up with. Hope and expectations was completely destroyed 🙁 . Don't get me wrong, the winning girl is okay but I can't help but feel like a choice made out of guilt, even though it's not. Can't say any more since it would be a spoiler.
I thought I could find solace in the anime... NOPE ... skipped about half of the heroines and completely rushed the Goddess Revival Arc with an ending that made it seem like nothing ever happened.
In short, It's a good read but find a good stopping point and pretend that the later chapters never existed or risk getting a gap in your heart.
On another note, If you want an MC similar to Keima, you might consider reading "Konjiki no Moji Tsukai - Yuusha Yonin ni Makikomareta Unique Cheat".