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This isn't really a full review, since as of typing this I have only completed sequence 4 of the game.
I'll get the comparisons between this and the earlier games out of the way first. Gameplay-wise, most of the good stuff from Black Flag is here, but you don't really get anything that hasn't been seen in previous AC games. You get new collectables, different weapons for your ship, and a new type of side mission and enemy archtype that reflect on Shay's role as a Templar, but there's nothing truly revolutionary for the franchise, such as a shitton of new gamplay features, the chance to build and operate your own Assassin Brotherhood, your own ship, or the ability to freeroam with your ship.
Story-wise, you do get a few things that make the game interesting to look at: the River Valley and North Atlantic locales, the Seven Years War setting and subsequent return to Colonial America, the chance to interact with past characters such as Haytham Kenway, Adewale and Achilles, and of course, the fact that you're on the Templars' side in this game and get to fight against the Assassins.
So far, my only gripe with the game is the reason it gives Shay (your character) for defecting to the Templars. In short, it's not because Shay comes to see that the Templars actually have good reasons for doing what they do that Shay agrees with, but because the Assassins get given the Ron the Death Eater treatment and the Idiot Ball and risk getting many people killed with their stupidity, prompting Shay to jump ship. Since Assassin's Creed III, the Assassin/Templar conflict has felt like less of a battle between good and evil, and more of a struggle between two opinions on what the world needs more. This game however, I feel it regresses back to the Good vs Evil days of Ezio's time, but switches the good/evil labels around, which I personally find disappointing.
In conclusion, this game is decent in its own right, and while there are a few differences between it and Black Flag, in terms of gameplay they're both very much alike. You guys decide whether or not that stops you from buying the game.
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