It's it the same as in reading a book about history?
No, that would be "en historiebok", or "en bok om historie".
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.
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.
Would this be correct?
Jeg drikker en historisk drikke
It would be more common to use 'drikk' in that case.
Jeg leser en historisk historiebok.