If you are thinking of buying Tetris Effect on PC you have to start downloading theEpic Games Store as the game is its exclusive. The title also offers a mode in virtual reality completely immersive. It seems however that this Epic exclusive will require access to Steam to take advantage of all the features of the game.
This does not apply to the traditional version in the game but, when you launch VR mode, maybe try it with your own Oculus Rift o HTC Vive, you will need to log in SteamVR, Valve's openVR solution. It's funny to think that an exclusive game mode of the Epic Games Store should use a technology from Steam, its biggest rival. Actually, access is not required as this is only a link between Valve's OpenVR API and the set used by the player.
In case you want to try a uniquely remixed classic experience, proceed with thepurchase of the beautiful Tetris Effect. Or, if you really don't like the Epic Games Store, you have to wait and hope that the game will also be released on Steam.