If you read Katherine Center’s books “The Things You Saved In the Fire” and “How To Walk Away,” check this short story on her website! http://katherinecenter.com/the-girl-in-the-plane/
I also did not know that the brother in “Happiness for Beginners” is the leading man in her new book (yet to be released) “What You Wish For.” Duncan is in both! I had no clue until the author told me on social media. I kind of read the book out of order.
I love it when authors do cross over characters and when you can read a book as a stand alone book instead of any given order.