Suggest me a book about the history of Norway, Sweden, Denmark, or even Ireland during World War II. Any other recommendations about the lesser known countries involved in WWII are also appreciated.

I recently found out out about the Osvald Group, but couldn't find any books about them that seemed positively reviewed. This has made me interested in books on Norway and other countries near Norway and/or with less known involvement in WWII. I don't know if anybody has any recommendations. If you do, please make sure they are in English. Thank you.