"The Unseen Realm" is a book by Michael Heiser that explores the spiritual world as described in the Bible. Heiser argues that many biblical texts reference a realm of spiritual beings, including angels and demons, which often go unnoticed in traditional interpretations. The book emphasizes the importance of understanding these unseen entities to grasp the full meaning of scripture. Heiser delves into ancient Near Eastern cultures and their beliefs, providing context for the biblical narrative and revealing how these spiritual beings interact with humanity and influence events in the physical world.