This book is a novel written by William P. Young. He wrote this as a Christmas gift for his children. He never had the intention of publishing this book. But when many of his friends and relatives read it, they liked it very much and advised him that he should publish it since it was a very nice novel. Thus he decided to publish this book. Young formed Wind Blown Media for the sole purpose of publishing this one book. The Shack has achieved its #1 best selling success via word-of-mouth and with the help of $300.00 web site; nothing else has been spent on marketing.
Mack is the main character in this novel. His full name is Mackenzie Philips. He is a father of five children. One day Mack takes his three children on a camping trip to Multnomah Falls and Wallowa Lake near Joseph, Oregon. There, while playing on a canoe, it flips and two of the children fall into the lake. While one manages to escape the other son of Mack almost drowns. Mack wastes no time and immediately jumps into the lake to save his son, leaving behind his youngest daughter Missy alone at their campsite. He manages to save his son. But after he returns to the campsite with his two sons he finds his daughter missing. Later, he discovers that his daughter has been abducted and murdered by a serial killer known as the "Ladybug Killer". When the police are called they find an empty Shack in the woods where Missy was taken but her body is not found.
The bulk of this book consists of Mack’s experience with the trinity. One day Mack receives a note in his mailbox from "Papa", saying that he would like to meet with Mack on that coming weekend at the shack. Mack suspects that the note may be from God, who his wife Nan refers to as "Papa". Mack goes alone to the shack. But when he arrives and finds nothing, he decides to go back. But as he leaves the shack and its surrounding place get automatically transformed into a wonderful lush and inviting scene. He goes inside the shack and finds manifestations of the Trinity into three persons. The God our Father takes the form of an African American woman. She calls herself ‘Papa’. Jesus Christ is a Jewish carpenter, and the Holy Spirit is personified as an Asian woman named Sarayu. Mack talks with Papa, Jesus, and Sarayu about Missy's death and his relationships with the Trinity. Mack also has various experiences with each of them. At the end of the conversation, Mack goes with Papa for hiking. Papa shows him where Missy's body was left in a cave.
As Mack leaves the Shack to come back home he meets with a serious accident. After he gains consciousness in the hospital, he come to know that he did not in fact spend the weekend at the shack, but that his accident occurred on the same day that he arrived at the shack. He also leads the police to the cave which Papa revealed, and they find Missy's body still lying there. With the help of forensic evidence discovered at the scene, the Ladybug Killer is arrested and put on trial.