Judaism is a religion but it is also a rich culture. Books of Jewish Interest will span fiction and nonfiction and cover subjects such as ritual, customs, lifestyle, mysticism, history, and cooking.
There is also a rich tradition of Jewish Fiction which makes sense because the Jews have a rich oral tradition and are storytellers. In fact, Jews are called the people of the Book but that is referring to the Torah.
Jewish Fiction will likely have themes related to history, culture or topics of interest to Jewish people but can certainly cross over into any reading audience.