No, it's an entirely linear game and there is no NG+ mode. I started it again for a few reasons. The first and foremost being that I really enjoyed the game and just want to keep playing it. I played it on normal mode the first time and now want to play it on hard (even though there isn't that much of a difference apparently) so that's a factor. I would also like to get the platinum trophy and need a few other random trophies from a second playthrough, as I finished the game with roughly 80% completion. Tbh I would probably be playing Assassins Creed Unity right now if it hadn't turned out to be a technical mess on PS4. To answer your original question, I'd say for most people it's a one time experience that you will want to revisit at some point in the future if you liked it.
Ha! I'm a fan of the AC franchise as well and was looking to pick it up cheap BF, but it's not on sale anywhere and even if it were, I've lost confidence that Ubisoft will truly fix its multitude of problems.
I'm a huge fan of the Alien franchise and I've said previously, in this thread no less, I'd pick up the game when it went on sale BF, but nothing makes me trade in or stop playing a game faster than game crashing/progress wiping bugs.
Thank you for your responses.