TLDR: This game is incredible though horribly flawed in a few ways. It is still worth a buy and playing if this type of game appeals to you.

Note: edited slightly after 8.0 Siege Mode patch

Space Marine 2 gets so many things right that the things it gets wrong are even more frustrating than they otherwise would be. A quick aside -- I enjoy the WH40K universe but I am not a giant lore junkie like some of my friends. That said, I have played a ton of WH games over the years. Being a WH40K fan is not required to enjoy the game.

First off, the things this game does right:
* The entire game is gorgeous, the environments are incredible, and the sound design is fantastic.
* You get to wield a great variety of Space Marine weaponry and most of it slaps HARD.
* There is a TON to unlock after the single-player game is done in Operations mode.
* Combat is INCREDIBLY well-done -- combined with the class, weapon, and heraldry upgrade systems the game loops work together to make an incredibly compelling whole.
* The execution animations are brutal and still fun even after dozens of hours.
* The game can practically be a Space Marine Heraldry Simulator -- there is a TON to unlock.
* Many new things for operations have been added since launch: missions, weapons, and enemy types. More are coming, even a new class and horde mode. (Edit: horde mode is out and it is SO SO GOOD)
* The modding community for this game is AWESOME. Look for the Astartes overhaul mod. You're welcome. :)
* Official mod support virtually guarantees this game will have interesting things to do for years to come, even when the developers wrap up.

Some of the things the game flubs a bit:
* Some of the dialog during the single-player campaign is ... just bad.
* The AI bots are fine for the campaign but they pretty much SUCK in the ongoing operations mode, especially as you increase the difficulty.
* There are several GLARING omissions in the heraldry selection, such as some decals only being available for the left pauldron or the right but not both. I am not an expert, but as I understand most of these omissions are not lore accurate. (Note: this will likely improve with future updates, this review was mostly written around patch 7.2 and later patch notes indicated major improvements are coming here)
* There are some niggling bugs that can be very frustrating, especially at higher difficulties where mistakes are incredibly punishing.

And the things that make this game wildly frustrating:
* Load times are unacceptably bad. Game launch to entering your first Operation can take well over 5 minutes, even on a good PC. I have watched task manager and nothing is particularly busy even though the loading progress bar isn't doing much. (I have had plenty of time to stare at it)
* You have to load into the game FAR too many times. I completely understand a big load when you launch a game, but the game seems to re-load nearly everything every time you return to the Operations hangar. Which you do after every mission. Or after failing to join a multiplayer game. Or after leaving a multiplayer game. You get the idea.
* Multiplayer matchmaking is an absolute travesty. You either start a game with a friend or 2 or you hope you get teamed up with someone. Unless you join a game where the class you wanted to play is already taken. Which you don't find out until AFTER you load into the mission. Or if you don't actually join an in-progress mission and instead show up at another player's hangar but they are AFK. Combine this with the load time issue and it can take up to 10 minutes to get into a game if you have to try several times to successfully join something. Why there isn't a list of games available for you to pick from or the ability to just start your own game is completely beyond me.
* And finally, these issues are intensified by matchmaking that just silently breaks which requires you to either return to the title screen (requiring two long-as-heck load screens) or quit entirely and restart.
* These 3 things combine to make for an INTENSELY frustrating experience. Normally I would just stop playing a game with this many negatives that reinforce each other, but the game is THAT good. It is STILL worth playing.

I want to end on a positive note -- this game is phenomenal. You can get around a lot of the matchmaking stuff by playing solo up to a difficulty you can manage with the AI or with friends / people from the official Discord server. At that point the load times are merely annoying as missions take 20-40 minutes to complete.

You can spend a silly amount of time just enjoying the Heraldry simulator. And then when you find a look that you like you can go punch a Terminid or a Chaos marine with your Power Fist. Or rip them apart with your Chainsword. Or blast them with bolter fire, a melta, or plasma ... your tools for destruction are legion.

This game really hits the 'giant super-soldier killing hordes of enemies' vibe and does an amazing job with the WH40K aesthetic. If this is your type of game, I really hope you pick it up so you can enjoy the carnage.