World War I
I'm currently working on book #3 of the Family History Mystery series and is to be called PICTURE THEM DEAD. It will be released in July 2015. The backstory for this one has a connection to WWI. It's been fun to learn some new bits of history and to search out my ancestors who were involved in that war.
If you have ancestors who participated in WWI, the New York Times is asking you to share your stories and family artifacts. http://www.nytimes.com/interactive/2014/08/22/world/europe/22family-callout.html?_r=0