Hard to tell really Wolf, i'll just list main features:
Stylised WOW graphics rather than realistic Witcher graphics, but similarly bright and lively.
Turn based combat, rather than real time manual skill based, but extremely enjoyable, interactive with the environment and exploitable.
A lot lighter atmosphere, and the humour is more whimsical than the Witcher.
More open areas, that you can explore as you wish, if you have the skill and will.
Not so narratively dense as the Witchers, but worth paying attention to still.
Very customisable characters, you can make whom you wish.
It's debatable but i'd argue that it's an even more living world than the second Witcher, equal to the first.
If that sounds good to you, then Bob's your uncle, Fanny's your aunt.