Interesting take on WWII
I feel there are 2 features this game has nailed very well. Alternate history and the production of WWII.
Alternate history makes the several playthroughs unpredictable which leads to a lot of replayability. From france going comunist to WWII starting because of a civil war in india, a lot of variety to it.
The way production is handled also makes the game very satisfying since your army will only have the resources you produced in the years towards the war.
While the game is very good it has 1 mechancs that need revamping. The naval part of the game currently doesn't work very well and it is extremely unclear if your fleet is winning or losing and if it is "helping" the war effort. Due to being a paradox game i ahve the hope that paradox will update this feature in the future.
While you can play with any country in the world, the base game offers a few countries with unique mechanics: France, UK, USA, Poland, Germany, USSR, Italy and Japan.
IMO those are the most fun countries to play with however if you feel you need more content you can always look at DLC which adds further countries that while small in nature are (relatively) relevant for the war, such as Yugoslavia, Romania, RAJ, china(s),etc.
IMO this game is worth buying for anyone that likes strategy games and WWII.