My favorite of the entire franchise and an awesome ending of Desmond's odyssey.
Connor is perhaps the most underrated AC protagonist: he has an badass design and his story is very, very interesting and entertaining. It has one of the best combat in the series, as seeing Connor brutally devastating his enemies is very cathartic. The Desmond sections are very fun, the open world is exciting and the ship sections can be tedious at times, but it was a cool new mechanic in the series.
Tree parkour is awesome.