Lol. I agree with historic book = book of historical significance, historical book = book regarding the past.
But can we get an 'AN' in front of both please?
Duolingo tends to use American English, in which words starting with non-silent "h"es do get "a" in front of them.
If Duolingo tends to use American English, then it should say "Write this in American English" in all instances. Otherwise it should use an in front of non-silent "h"es
so you only put the special o in when 'bok' is plural? can someone please explain this? (sorry for my lack of linguistic language, I don't know what the special O is called)
Basically yes. Bok - Book, Boken - The Book, Bøker - Books, Bøkene - The Books.