How long is it in total?
Like breh said, around 20. I beat it around 35 but I also had a few quests I didn't complete. Also keep in mind there is 16 Unique monsters to kill.
Also there is "slates" hidden around the game that you collect. A couple hours into the game there's a beach area with a cave. You use the slates to unlock parts of the cave. Each part you unlock has treasure and the final part of the cave lets you unlock 4 more Unique monsters.
So....yeah. There's a gang of stuff to do. The only advice I'll give you is focus on building Community because towards the end of the game you need a certain Community level to progress.
Fred.