The official Japanese twitter account for NieR: Automata has announced that the game has sold over 3 million physical and digital copies worldwide. The game had just passed the 2.5 million milestone in March, so that's quite a lot of sales in only a few months.
You can check out the official tweet below (via IGN), though it's entirely in Japanese.
— NieR公式PRアカウント (@NieR_JPN) June 6, 2018
Interestingly enough, today is also game director Yoko Taro's birthday. And Taro shares his birthday with the protagonist of NieR Replicant. Taro directed NieR: Automata, as well as NieR Gestalt and NieR Replicant.
NieR: Automata was a major success for publisher Square Enix, but more so for developer PlatinumGames who had a string of poor releases and the cancellation of Scalebound in early 2017. So they desperately needed NieR to do well. And it did. In fact, Automata may have single-handedly saved the studio.
We gave Automata a 9.5/10 when we reviewed it last year, calling it a "hack and slash game at its best." Though we did note that:
"… there are just so many ways to play this game that no review is ever going to do it full justice. If you're a fan of action titles and don't mind taking the time for an impressive story, this is definitely a game you need to check out. Play it a few times, unlock a couple of the endings, really get a feel for how the game works and the way the world unfolds, try out different characters, different mod kits. This game is pretty damn magnificent."
Currently, the developer is working on Bayonetta 3 for the Nintendo Switch.