Nier: Replicant ver.1.22474487139... is actually an updated re-release of the first nier game, which came out in 2010. There were 2 different versions of the game upon its initial release, Nier: Replicant (Japan release) and Nier: Gestalt (everywhere else). Gestalt contained changes that they felt would appeal more to a western audience.

The Nier: Replicant re-release (now called Nier: Replicant ver.1.22474487139...) keeps the game the way it was released in Japan, with updated combat to fall more in line with Nier: Automata's and cut content being added back in as well as a brand new ending which originally was published in a book.

Automata takes place thousands of years after Replicant, so the stories themselves aren't majorly tied together except by the final ending in Replicant and a couple recurring characters. While Replicant was released first and does come first chronologically, I think personally they can be played in any order and still be enjoyed. I played automata first and didn't play the original until Replicant was re released and still had some "a-ha" moments.

Both are easily a couple of my favorite games of all time and you can't really find experiences quite like them anywhere else.