Addicting, great hack and slash
You have a huge selection of gundams (not all of course), you can pick pilots and level/master them. Loads of quests, if you pay attention to the story, it may be quite interesting, if not just have fun and enjoy!
The only gundam series I have ever watched was G Gundam, luckily they had some characters from that series, which made it more fun for me. The fighting system is repetitive, you can use certain combos for different situations. Simple as this, if you get bored, you can just pick a different gundam and they will have different attacks.
The other thing I will like to note, is that pilots have access to gundams that normally (in anime/manga) they won't use. So it isn't restricted to a user. I find this a good idea, so people don't need to spend extra time to level a pilot to find out that they can't use a certain gundam.
The upgrade system in this game is interesting, basically there's a mobile suit lab. You can send in parts and after you complete a mission, they will come out better and stronger. You can add perks to the parts to make a certain gundam stronger. This lets the player feel like their time is being used well.
There are skills that can be unlocked after a mission, which a certain percentage. This is a fair system, so people have to work hard to get certain stronger skills.
Overall, If you like Dynasty Warriors, God of War, DMC, I guarantee you will like this game! If you are curious, just look at some gameplay. I wasn't a big fan of Gundams, and yet I still find this game entertaining!