JA2 takes place in a war torn country where an bitchy dictator rules with an iron fist. You can send her flowers if you'd like. You are in control of a small mercenary company, and you capture towns and mines as you slowly take over the country. As you take over towns, you can also train troops to guard them and in the new version, they even go out patrolling. It's open ended, so you can go after whatever territory you want, in fact you can even make a beeline straight for the capital (although that's not very easy without cheating to get great mercs.) As your mercs fight, they increase their skills, meaning the mediocre ones can be very effective by the end of the game.
The setting works, but it's the characters that really bring JA2 to life. The mercenaries all have very unique personalities, many bordering on psychotic. They are extremely entertaining.
The combat is some of the best turn based combat out there. It's similiar to Xcom or Silent Storm, although I'd argue it's still better than either. The weapons and equipment are extremely detailed and it really feels like they accurately depict the variety of ammo and weaponry in a modern warzone. Equipment is a big concern, and it's common for my mercs to have an aussault rifle or two, a couple grenades, a backup sidearm, and even a knife or two.