The Aveline DLC was released alongside Assassin's Creed IV: Black Flag, providing an extra 60 minutes of gameplay just for owners of the PS3 and PS4 version of the game. It's a new standalone story that brings back Aveline, the protagonist from Assassin's Creed III: Liberation on the Vita.
I couldn't recommend it, though. Liberation brought in some interesting ideas and commentary on being a black Assassin in 1765 New Orleans. This add-on feels more like a reskin of Black Flag only without the exploration or collectibles. Yes, Aveline retains her own animations and the brutality of her machete kills is still very much apparent. Her personas never make an appearance though, so you're left with just her standard Assassin garb and the mechanics from IV – blend into bushes, shoot darts, sabotage alarm bells and drop onto unsuspecting guards from a tree branch.
The missions are totally story-driven, which isn't a bad thing in itself. However, across the three memory sequences, the story doesn't have a whole lot to say. You'll start by sneaking around forts and plantations, incapacitating guards and freeing prisoners. This is followed by a long climbing stint through caverns and buildings. These are staples of the Assassin's Creed series and all enjoyable things in themselves. If all you want is more of that, then have at it.
By the time you reach the end though, the story just stops. You search for a thing, you chase some people, you reach a goal and then bang, you're done. No revelation, no extra insight, no character growth. It's just an extra hour of the same land mechanics you get in Black Flag. If the plot was a set-up for future storylines or clever follow-up to a passing mention in Black Flag then I'd be impressed. As a standalone piece, it just feels extraneous