The story gets better from chapter 40 onwards, I think, as it focuses more on DxD characters and world building.
Kuuhaku_28:the plan is good, but if it's too slow it'll get boring for a long time, at least there's a time skip, not too long in elementary school (sorry, I've only read about 30 chapters, maybe there will be a time skip in the next few chapters, I don't know)