Battle Brothers

This is a rough recommendation because what makes this game great also makes it a terrible choice for many gamers.
The fact is, this game hates you. Much like Kenshi, Quasimorph and many other games. This game is brutal. That's not the same as being hard. Technically the fail condition of losing all your brothers is a pretty high threshold. But this game makes you feel like you aren't making any progress oftentimes even when you are making a little bit. Doing a contract where you lose 3 brothers all at once for a reward that doesn't feel anywhere near worth it isn't exactly uncommon. The economy is also fairly tight. You can get ahead of it if you know what you are doing, but between low contract pay, mercenary upkeep, equipment repairs, buying overpriced gear, replacing consumable items, replacing dead mercenaries, and settlements giving you terrible prices on your sold equipment, it can feel like you aren't making progress even if you play fairly well.
To top it off, the non-human enemies can actually be frightening to fight even with the art-style divorcing you from the action. Being used to fighting bandits or barbarians, only to switch to an enemy like Unholds (giants) who will literally toss your brothers around like ragdolls and recover health each turn, or lindwurms (poison dragons basically) who will burn your brothers with acid every time you damage them. Even zombies (called wiedergangers here) can be a legitimately difficult fight, with them popping up with around double the enemy numbers, having no fatigue or morale mechanics, and occasionally getting back up again once killed.
That said, the brutal nature of the game can make mastering it feel amazing. You'll laugh your butt off when you are killing gangs of 3 unholds by trapping them in nets and poking them with spears, knowing full well how terrifying they were when you first fought them. Once you start taking on the secret bosses or more dangerous monsters, or even better when you resolve an endgame crisis, you'll think back to how hard everything used to be and realize how much progress you made.
Also the setting is fairly interesting. I hope they return to it someday with a future game. There's actually a tie-in comic you can read on steam.
If you like tactical turn based simulated games and you want them to hurt you until you love it, this is a game for you. Otherwise this is a hard game to recommend.
I also recommend picking up the beasts and warriors of the north DLCs. They add some interesting encounters, different mercenary company types, and actual incentives to fight beasts who otherwise are a fairly low reward enemy type. The Blazing Desert DLC is expensive, and while it adds a lot to the map with many new contracts and enemy types, it's also a region you might very well completely ignore in the average playthrough unless the holy war endgame crisis kicks off or you pick an ambition that rewards you for traveling south.

Played nothing else for years! 5500+ hours in and still hooked. I wish for more DLC:s and official content other than mods. re-playability is great!

Really fun game, but...
The only problem is there are so many anti-tactical things that stop you from being able to plan. "If bad luck makes your plan fail it wasn't a good plan" How am I meant to make a plan when I have no idea on the terrain, very limited troop placement, inconsistent enemies and task difficulties and vague mechanics. It's a shame because it's a really fun game and I would recommend it but the steep learning curve also comes with a frustrating realisation that the game is more shallow that you think it will be.

It's... so good... SO, SO GOOD. You can really appreciate how well tought everything the more you play it. How you discover little strategies, and how to beat whatever random smuck wiped you out last run. Distinct enemies actually matter and play differently. Just in the same faction (Undead) you have. Skeletons, who always move last but won't tire out: They are all with shileds and will play the long game to eventually tire your brothers. Zombies: Easy to kill, but they are a lot, and I mean A LOT. They respawn if you don't decapitate them. Ghosts: Stand in the back and spam fear so your brothers flee. Without being able to control them, they're as good as dead. Die in one hit. The catch? You have to take the horde of zombies separating you WHILE they spam fear. Not only that, you have a fixed 5% chance to hit them with ranged, forcing you to go close.
You see them, you die slowly and horribly... and then you learn. Skellys have shields? No matter, axes break them and flails ignore their defense bonuses. Zombies respawn? Not if you use cleavers, that always decapitate enemies. The ghosts make you unable to control troops? Go from 2 sides, since their attack is a kind of cone that can't hit everything at once. Also use the skill RALLY to give morale to your fleeing brothers. THE WHOLE GAME IS LIKE THIS.
The bad: This game is NOT for everyone. Losing company after company hurts, specially when you started to like your bros. They can get permanent injuries, wich almost always means you have to dispose of them anyways. I wish we could treat them, even if costly. It's sad to have to push them away and you'll slowly de-humanize them, like disposable tools. I don't want to play like that man.
The other problem is skills. While Bros are clearly NOT made equal, everyone has access to the same skill tree. Sadly, some skills are REAL bad in comparison with others. Some examples are Brawny, that should really give you more that what it gives, and that the best skill that you could pair it with, the light armor expert one, specifically states that doesn't apply. I think buffing these "low tier skills" would do marvels for the build creativity.
The other is the weapon expert skills. You basically specialize your bro in one type specifically. The problem is that some weapons, like bows and crossbows, are usable in only certain scenarios (skellys are almost inmune to long range for example) and a lot of times it's best to just use the type of weapon the enemy is specifically weak to. This is kinda aliviated by the fact that you don't always know what's jumping at you in the middle of the forest at 3 am, but still.
So yeah, absolute marvel of a game, losing is fun, buff ranged and low tier skills please. Fuck you Hoggart.

This incredible game, despite playing for hours, the different events I encountered in every playthrough prove the level of replayability. The RPG elements are really high quality. In my last save, I saved my banner man from execution by the villagers, when I asked about his story, I learned that he was caught r*ping a watermelon. We fought side by side in countless battles in my band for months. We lost him in a brave battle against the Orcs. You are missed, Gero The Melon Mugger.

Summary
Battle Brothers is a fun and rewarding experience IF you are willing to invest time and effort.
By time, I mean you'll probably spend the first 4 hours figuring out all the different scenarios that you'll encounter.
By effort, I mean you need to learn from different guides explaining the game's systems.
This is more of a planning and resource management game rather than a combat focused game.
If what you’re looking for is casual fun, play on the easiest difficulty, because even normal difficulty will cause you problems if you don’t understand the systems properly.
Check out CarveaHole, FeedingFriendly, and FilthyRobot on YouTube for guides.
What to expect in terms of gameplay
You would think that combat is the focus of the game, but its more like the "proof" if your plan works.
Planning is a significant part of the game that reviews don’t talk about.
Determining the direction to go when exploring the overworld.
Checking each mercenary’s stats and spending skill points.
Equipping appropriate gear on your mercenaries.
Evaluating the risk/reward ratio of contracts.
Post-Battle analysis
These are activities you will do A LOT, especially in the early-mid game.
Skipping over these will hurt you in the long run.
Resource Management is another significant part of the game that reviews don’t talk about.
Money
Gear durability
Food
Medical Supplies
Mercenaries
These are resources that you have to properly manage, especially in the early-mid game.
Resources are more important than combat. Certain enemies become irrelevant when your mercenaries are decked out with strong gear.
If it sounds like a lot of information, that’s because it is, and we haven’t even talked about combat yet.
The combat mechanics are based on dice rolls.
You can really get screwed over by the dice rolls in the game. Risk mitigation is the best way to approach combat. Rolling for a 50% chance is exciting, but not a reliable way to play the game. This will lead to you not playing the game how you want.
Want a mercenary to become a 2-handed axe wielder? Too bad, he will probably miss more than half his swings, and since he doesn’t have a shield, he’ll die after missing his attacks.
Objectively speaking, spears and shields are the most reliable way for you to get out of the early game.
Cool-sounding builds will only come online somewhere during the mid-late game.
Reward
The systems I’ve mentioned above do interlock in a satisfying way once you’ve gotten the hang of them. Struggling through the early game with your mercenary band and slowly building them up to defeat the late game crisis is an experience that this game uniquely offers. Cliche as it may sound, this game is about the journey, not the destination.
The price for this reward?
Learning the game’s systems through guides, and applying what you’ve learned through trial and error.
Play on the easiest difficulty if you want to roleplay and live out the mercenary fantasy :)

I have an obscene amount of hours clocked in this game and an itch to put in more that I have to suppress otherwise I wouldn't get much experience playing other games.

The game has a pretty steep learning curve, does not hold your hand, or offer much in the form of guidance. But it is oh so rewarding when you do get the hang of it and are able to take on the more challenging battles the game has to offer.

My favorite Turn-Based Strategy game ever. If you're on the fence, play this and profit.