Michael Heiser believes there is an unseen realm that is just as real as the computer monitor or smart phone your looking at right now. This unseen realm is made up of spiritual beings we normally refer to as angels and demons. Heiser’s goal is to help you read the Bible with a biblical worldview, or as he puts it:
“My goal is simple. When you open your Bible, I want you to be able to see it like ancient Israelites or first-century Jews saw it, to perceive and consider it as they would have. I want their supernatural worldview in your head … Seeing the Bible through the eyes of an ancient reader requires shedding the filters of our traditions and presumptions … I want to help you recover the supernatural worldview of the biblical writers.” (The Unseen Realm, 13).
I’ve read a decent bit about the “unseen realm” (I wrote my dissertation on Paul’s view of the principalities and powers). Heiser’s books are two of my favorite treatments on this topic. He does not blush when the Bible describes things our society sees as silly superstition. At the same time, he does not advocate a silly warfare approach to the unseen realm. Additionally, Heiser has put this material into two books. The Unseen Realm is longer and more in depth, and Supernatural is shorter and more to the point. Both are accessible to adult readers.