First of all I see a lot of butthurt people here, who are complaining about the promising start and the mediocre rest. To be totally honest I understand what they mean, the story makes a large change in genre, it goes from gritty survival story to harem romance fantasy. I see where this frustration comes from but just BE AWARE OF IT, if you are not looking for a fun romcom adventure then don't read it or just read until they get a special ring (you'll know) and imagine your own end.

Now that I have clarified why it isn't justified to complain about it becoming a harem, romcom... well, whatever... let's get into the good and the bad.

Good
-It is not a traditional harem (I usually don't like harem). There is only one love interest and it's clear form the start that they are meant for each other. Unfortunately the MC is so dependable that others start to make moves on him, which makes for good comedic moments.
-The characters are very likable.
-The character development, the MC goes through is not something we usually see in isekai and it makes the story a lot more interesting. (it reminds me a lot of Kaneki from Tokyo Ghoul or Eren from Attack on Titan)
-The power system is rather well explained in regards to knowing who is stronger than the other
-The world has extensive lore in regards to politics and religions which makes the story even more engaging

Bad
-I read more manga that LN so I'm unsure if it is really a bad point but... There are very few illustrations, I personally would like more.
-Even though I've said the character development of the MC is interesting, it still isn't as prevelant as I would like and for a lot of the supporting cast it is almost nonexistent.
-Although the power system makes it clear who is stronger, the magic system is not explained in detail and makes it feel as if spells and such are pulled out of someones ass.
-The usual issue with the OP MC, however large institutions (nations, church) and the like are still regarded as a legitimate threat which gives a sense of realism.
-The antagonists are explained, however not in as much detail as I would like
-The Goal sometimes seems like more of an excuse to further plot than an actual necessity

TL;DR
It is an enjoyable story with a cool romance and some fun harem aspects.
Although the world has gaps in its lore the overall world building is nothing to scoff at (it really is rather well done). The characters are lovable and make the read that much better. The moral ambiguity of the MC makes you question him, which makes the story quite engaging. All in all I can recommend this read to ANYONE WHO ENJOYS SOME ROMANCE IN FANTASY.

To anyone who is just interested in a survival story just read from the beginning until the ring opens a door and imagine your own end.