Suggest me books for my parents who just took an European vacation earlier this year

Hi there!

Doing some holiday shopping for my parents who just took a big European vacation earlier this fall. They visited Paris, Normandy Beach, Colmar, the Swiss Alps, and took a river cruise in Germany. Any fun books for them to read that take place in these locations? They enjoy mystery, thriller, historical fiction books. I did get my mom The Women in the Castle, but looking for more suggestions.

Thanks! Happy holidays.