Disclaimer
This review of the DLC will be as unbias as possible and won't be as in depth as the game review which will have a link provided. If there are changed to the gameplay made by DLC either in provided story missions or other things then I'll explain as such, and I will go over other things in a similar fashion. There also will not be a score and will be talked about as a recommendation for people who have already experienced the game, even if the DLC is better then said game. Also since I've only reviewed the single player portion of the game, the DLC will be no different.
Assassin's Creed IV Black Flag Review
WARNING possible spoilers WARNING
There are a few things unlocked in the main story missions like being able to do small missions to gain weapons and outfits from famous pirates particularly like Captain Henry Morgan (my personal favorite pirate) as well as unlocking some cool decor for your ship. Outside of that, you can unlock weapons and outfits from previous, and if you count Connor and the timeline, future assassins (Ezio, Altair, and Connor). The largest draw here is of course Freedom Cry.
Freedom Cry is a continuation of campaign where you get to play as Ade', the first mate for most of the main game and best friends to Edward Kenway. Ade' is now an assassin with his own ship but he crashes in an area where slave trade is rather heavy which, being a former slave himself, sets Ade' off a bit. He ends up ditching his assassin duties for a while to free slaves and maroon rebellions and help them, however things go wrong in the end. The story is okay, it isn't exciting and little actually happens at the end which is disappointing, but it is cool to see what happened to the Jackdaw after Edward retired from pirating. Also Ade' is cool to play as, especially if you have watched the cartoon Boondocks on Adult Swim and know the story of Catcher Freeman, because Ade' is the pirate version of him complete with a large machete. the only issue is in the story mode besides the lackluster plot, would be that Ade' is slow, so slow that often times he gets hit due to being stuck in an overly long kill move. If he gets hit in the kill move he often doesn't complete the kill either which is disappointing, and his fighting style slows down more while raiding a boat, a problem Edward had made worse because of Ade's already slow movements. The levels are designed more with stealth in mind however, but when Ade' has to listen in on a conversation he has the worst luck due to stupid things, which makes those missions also a bit frustrating.
This DLC could be so much more then what it was. Ade' is a cool character, and it is great to see him as well as play as him since he has a cool fighting style, but since his style is so slow he takes damage easily and the gameplay slow downs that already happen are just worse here. The plot is also rather boring, you are basically freeing slaves and maroons for a rebellion which is good, but the main story missions Ade' does aren't really that lasting nor do they seem important. Things do get done, but not as much as need be to really resolve anything.
If you like playing as a black man freeing slaves from white men, this DLC is easily something you need to look at. If you like Ade' because he is a cool character (which I feel he is), then this is worth a look, if none of those make you want to spend the money, then wait til it is on sale. It isn't bad and it does have fun moments for sure, and the things for the main campaign is still pretty cool, but it doesn't affect too much other then looks really cool. If you want all the DLC for single player it isn't something to really jump on, and even at sale price it isn't that great, but for the season pass, 10 dollars is worth it more then 20 dollars.