It is a shame this game is currently rated below 4 stars and sold for SO cheap, you might think it's some utterly failed crap.
While I can't judge the GOG version itself (I own it on Steam), I can say it is a great game. It continues what the Enemy Within expansion did for XCOM 1 and gives you many ways to customize your soldiers with equipment and skills. A major component of XCOM 2 is, that many mission need to be fulfilled within a given limit of turns (which was also stronger emphasized in the XCOM 1 EW).
People have mixed feelings about this. I personally like the time limits, as it forces you to take risks by quickly advancing instead of playing it safe by slowly advancing with overwatch. This is balanced with a slightly more generous health pool of your soldiers and the fact, that there are more skills which allow you to kill several enemies with one soldier per turn. This requires a proper setup and can really turn the battle around. So satisfying when it works!
The War of the Chosen expansion even changes up the smaller DLCs previously released and incorporates them into the expansion. The lord aliens offer a unique challenge, as they get an additional move for every action a soldier takes. "Free" actions and stun items thus become much more useful.
The Chosen have each unique abilities and random strength and weaknesses each time you start a new game. They can randomly appear in any mission and can kidnap your soldiers, which keeps you on your toes.
If you can defeat any lord or Chosen, you are rewarded with powerful unique gear. Because you get only one of each, you better be careful not to lose them if your soldier gets downed, kidnapped or did not evacuate!
In general, XC2 forces you to think much more about how you spend or collect ressources and puts limits on everything. Even if your soldiers are not injured on the mission, they become tired and you have to rotate your roster.
And the "propaganda" storyline is more topical than ever!
