The Ace Attorney - Spirit of Justice (or Gyakuten Saiban 6) prologue is a really good introduction to the sixth main series Ace Attorney game. It does a solid job of setting up what needs to be known, for both returning fans, and first timers as well. It's also the first proper reintroduction of fan favorite Maya Fey, now all grown up into a adult, although first timers will likely be a little confused if they hop in completely blind, as to a lot of who she is and what her and certain characters are talking about, since it's based on already long established lore.
But you really shouldn't be jumping into the series at this point anyway. I'd definitely recommend at least checking out the Gyakuten Saiban: Sono "Shinjitsu", Igi Ari! anime, which covers quite a bit (if not all) of Maya's backstory within it, if you don't want to play the actual games that come before.
Anyway, overall this is a solid prologue. It reintroduces the important characters, introduces the important new ones, sets up the concepts that fuel the game, and generally just does what it's meant to in a well executed manner. My only real complaint is why this wasn't included in the actual game. Which instead starts by throwing you straight into the events that happen following the prologue, without telling you about anything that happened in it.