Assassins Creed Odyssey is absolutely brilliant. It's such a vast improvement on the previous AC games I've played. It's stunning to look at, the missions are varied, the combat system has been revamped and is miles better, the characters are really good and it's absolutely vast. I really like the story too - they've paced it well and when things open up, it's pretty exciting. The number of side quests are ridiculous, and that's a good thing because the XP you earn for completing them helps you to level up quicker which you need for some of the main story quests.
I'm taking my time with it but I'm 16 hours in and I've only visited 8% of the map.
The main downside is that I keep wanting to do 1 more side quest before I finish which means a lot of very late nights!