I have a hard time alternating fiction with non-fiction when the last fiction book I read was a really good one. If it wasn't, that is when I move to non-fiction.
Also, if you are looking for non-fiction that is decent read, try Erik Larsen. Earlier this year, I read In The Garden of Beasts. It was really interesting. It is about the ambassador to Berlin(and his family) during Hitler's rise right before the war.
Also, Devil in the White City was really good.