To recap for those who aren't familiar, this DLC takes the main characters of Bioshock: Infinite to Rapture, before it fell into chaos.
If you have the season pass, then you're done-- just download the update when it's released and start playing. Otherwise, it'll set you back $15, as will the second episode. If you're fairly confident you'll want to play both, the season pass is $20, so more bang for your buck!
I want to dig into Infinite since they got the Mac port but I am pretty backlogged on games as is and with Terraria 1.2....
That said, Infinite wins the award for prettiest game of the year, in my book anyway.