I actually liked the writing style a lot and found the month at a time time jumps were done pretty well - something that usually frustrates me.

Likeable FMC but kind of debatable for the rest of the harem. The point of the story is that they were an unusually and reluctantly formed group BUT I was waiting for the point where they all realised the value of their woman. At no point did they seem to have  the realisation of how lucky they were to have this 'rare' female in a dystopian world, who happened to love, cherish and fight for them. 

Some of them are actively talking about leaving her or if it's worth it and if she prefers others in the harem months into the relationship when she's given them her body and soul AND saved their lives AND done nothing but love them.

The characters have a lot of flaws, that's certainly their charm, and they do somewhat evolve. But they generally only behave under the 'leader' of the harem which doesn't make you feel like you're dealing with adults.

Also this has the BIGGEST dead wife trope you'll ever read I'd imagine. I'd avoid if that's not your thing.

Wife is actually alive. MMC leaves FMC to go and find wife, then wife dies on page.