What audience would you recommend Dear Missing Friend to? Is there another book or author you feel has a similar theme or style?

What audience would you recommend Dear Missing Friend to? Is there another book or author you feel has a similar theme or style?

I think this could be YA as well as adult level and for readers who like historical fiction based on true events. I can’t remember an historical fiction book I read that was told through letters. I believe one of Ruth Ware’s books was told through letters - I read that and found it a good story.