Ahh, the first light novel I've ever read, and my first (well second, technically) ecchi as well! A story where I initially read/watched it for the PLOT
but then became engrossed with the actual plot. I'm surprised it's been 2-3 years since I last read it!
Sure, it's not the best in terms of story or art, but I'll be damned if I didn't have any fun reading it! The story is interesting, the relationships are satisfying, the characters are enjoyable, it flaunts it's ridiculous sides with pride, and it has some pretty good fights for it being a story about a man's journey to becoming Harem King. I always found the world-building interesting, with details of reincarnated devils and angels, the culture of low-, middle-, and high-class devils, the pawn class system, rating games, etc.
I suddenly stopped reading for some reason, leaving off at volume 14, and I never found a reason to continue reading again. However, with the fourth season of the anime, Highschool DxD Hero, coming out soon, I may have found a reason once more!