Iceland's a beautiful place: it and the Faroe Islands are the most beautiful places I've been to. However... can't really understand why anyone would prefer to go there in winter rather than summer. It's only light for about 3 or 4 hours in December - all that natural beauty and you can't see it 'cause it's dark! Northern Lights are stunning if you can see a good display, but they don't take bookings unfortunately
Anyway, back to NCL matters...