Disclaimer: if you don't like incest, S&M play, or any other kind of kinky sex play then you shouldn't read this (it doesn't have ntr though). Though if you can ignore those scenes or they don't bother you (like me), go for it.

FYI: the mc might seem dense and the usual beta mc from the Japanese novels but trust me, this guy is amazing at his "job", just give him until volume 2 or 3 to judge his character.

Review with some spoilers below:
This Light Novel has a generic story where you have a guy with an ability that only women should be able to use, just like in IS: infinite stratos for example, and from there the story revolves around these machines that they can pilot and this energy that they need to be able to pilot them. Said energy can only be recovered through ecchi acts, of course. The plot is actually decent-ish for a harem/ecchi novel and it can be divided into 2 parts:
Volumes 1 through 7 and Volumes 8 through 13. Volume 14 was written later just to tie everything together, which I think it perfectly did.

The 1st 7 volumes talk about AU collisions that were happening on Earth (Lemuria). This collisions connected Lemuria with another world called Atlantis and that obviously caused war and troubles because of various circumstances. We get introduced to 90% of the characters in this long arc and get to know them as the conflict escalates. If you don't enjoy the story up until this point, then I think that you should stop reading, because the arc that coms next isn't that great in my opinion. Though volumes 4 and 5 also had some "weird" (to say the least) things happening that people weren't a fan of.

From volume 8 to 13 the story moves to greater threats and goals and because of that the story gets a bit more serious, not much tho, aside from that at this point the ecchi scenes are also a bit repetitive in my opinion and although it didn't bother me much and I still enjoyed a lot of people were disappointed with them.

I think the author finished the novel quite well, even though if he wanted to, he could probably still make 1 or 2 more volumes.