It's fun at the beginning, but as you play you notice that the quests are very similar to each other and it's starting to be a little boring. Most of the quests require you to go to some cave/tomb/ancient repository, fight some monsters/bad guys and retrive some relict/book/treasure/knowledge. And that like 2/3 of the game. There is a really big open world and most of the time you have to spend in some dungeons. The world itself is filled with an enormous amount of repetitive activities such as Merlin Trials and it feels pointless to do them really. Also I am not a fan of rescuing magic creatures and taking care of them, but maybe it's just me.
As for the plot, I found the Sebastian's quests more interesting than the main quests. Other side quests for Natty and Poppy are really mid.
The combat system is nice, especially when you learn unforgivable spells, but it feels really strange that you can use them without any consequences.