Warframe is a amazing mastery based multiplayer game.
You can choose from hundreds of weapons and 29+ warframes.
The good part is that you can mod those however you like, you can choose from thousands of different mods.
The game has some grinding elements but the developers are trying to get away from grinding in the future.
New stuff is added everytime, DE updates the game regularly with more stuff for you to collect and balances to weapons and warframes.
You can play with up to 3 friends and there are a lot of gamemodes so you won't get bored, if you don't have friends don't worry, there is a good matchmaking system that will find you a party to play with.
You also have a campaign and a lot of bosses to beat.
Don't get scared by the premium currency, the game is TOTTALY not pay2win, a paying user has nothing over you, you can get anything without money.
As a player with 300+ hours i never added money in to the game and i managed to get all the prime warframes and 1500 platinum cash just from trading.
Go ahead and install the game i am sure you will like it, get a friend or two to play with you, start your space ninja adventure today, good luck !