Comedy and Isekai. If you're looking for something unique but not terribly deep, this series is for you. It's an easy read for someone who isn't afraid to have fun. I say the series is unique, but it uses tropes constantly. So how is it unique? The main character is aware that he is in another world, but he doesn't want to stand out. So he himself uses tropes that he is aware of to appear as generic of a character as possible, all for the purpose of supporting what "should be" the main character of the arc from the shadows. If you were reading adifferent book from the angle of the "should be" main character, this hypothetical MC would be doing normal MC things and then this absurdly powerful shadow assassin would come in, say a one-liner that doesn't make sense in the context, and steer the fate of world through his actions, all to disappear as fast as he came in.

The parts where he is trying to be a background NPC are generally the light-hearted comedic parts. Between the lengths Cid goes to in order to intentionally appear weak or stupid and his true greedy and mukky personality popping up at times, it's easy to grin as you watch him lead everyone by the nose.

The parts where he is Shadow is the real meat of the book. The pacing is well done, but the most important thing in my opinion is that the book takes itself very seriously for these parts, and I think that's what makes it shine. It goes above and beyond "chuunibyou" levels for sure, yet it still takes itself as seriously as non-fiction, which lends itself to still being part comedy. It's essentially a parody of the generic powerfantasy harem isekai, yet is a powerfantasy harem isekai itself. The book describes Cid's ability as absolutely perfect beyond human level, yet it's all believable in the scope that it presents itself. This is where I think the book/series is most unique, in that it can use these known tropes to its advantage to launch itself to new heights.

I won't talk about any emotional/dramatic aspects that are present because it's hard to get into without going into spoiler territory. But I will say that because the book takes itself seriously a majority of the time, I found myself with watery eyes in a few spots, which I think is the perfect amount. If I remember correctly, it might have been once per volume (maybe less?).

I would finally like to mention that in some cases, the book will let you come to otherwise conflicting hypotheses for certain scenes. I'm not saying you need to take notes or something, again it's not <i>that</i> deep. But thinking "Hey didn't [character] say the opposite earlier?" is pretty normal and heightens the investment I had while reading. So if you're not exactly paying attention, this may also be lost on you.

Overall, it's a solid, dumb-fun book that's easy to read through and each volume starts and ends its own arc so you can stop whenever you want.