Yes, the series might have some incorrect historical events or incidents. But if you love great adventure-drama, this is a good production. And TV-series dosent have to be perfectly accurate according to history anyways. It's set during the second war in Norway, following the royal family. Acting and writing is in good quality.
I would rate it 8/10, but give it a 10 - because of the unfair rating people give only based on some fake events.