Rokujouma no Shinryakusha is much more than it seems at first glance. Starting this novel I expected average harem and instead got greatly written story with incredible characters.
Story setting feels very ordinary at first: normal boy starts living alone in a cheap apartment. But with every girl introduced it becomes more and more crazy. It actually gets to the point of being pretty ridiculous, but, surprisingly, story never becomes random and there are no plot holes. Author does great work at connecting all loose ends and foreshadowing events that will happen much later. Nothing happens without a reason.
The most important part of this story are
characters. Not only because it's a harem, but because whole storyline is build on their stories. Unlike usual harem where backstories of heroines are just side chapters and main plot is focused on single girl, Rokujouma no Shinryakusha connects all, seemingly unrelated, stories into one great, detailed and epic story with some good character-based comedy.
Characters themselves get a lot of development. They discover their past, defeat their weaknesses and mature. All the girls have good reasons to be in harem and those reasons often evolve as they mature.
At the center of the story is our protagonist - Koutarou Satomi. He is just normal, and I mean that in a good way. He isn't one of those "good at nothing, but nice" guys, nor is he someone with hidden dark past. He has his strengths and weaknesses balanced in a way that make him feel believable - you can actually imagine person like him living next door.
Author made great use of Koutarou as a focal point of the story. He becomes catalyst for other characters development as he gradually uncovers their stories and help them overcome obstacles. That normal boy, by getting involved with with invader girls, becomes main character of their respective stories and connect them in most unpredictable ways.
Writing about art in novel might sound strange, but Rokujouma no Shinryakusha's illustrations deserve a mention. The way characters are portrayed in them helps a lot with imagining their actions and expands on author's character building. Their looks fit their personalities perfectly.
What I can say for sure is that Rokujouma no Shinryakusha is the most enjoyable novel I've read so far. Great story moving in the most unpredictable ways, awesome characters that never stop developing and very solid protagonist at the center of it all makes reading this novel a pure pleasure. I don't remember any boring moments or stupid decisions made just to push the plot. When it comes to enjoyment, I'd say Rokujouma no Shinryakusha is simply flawless.