I thoroughly enjoy all of Ted Dekker's work, and Green is no exception. This is book zero in The Circle series, which also consists of Black, Red and White, and also ties into the Paradise novels: Saint, Sinner and Showdown. This book is the beginning and the end of the series. In these novels, a man named Thomas Hunter is able to, for reasons unknown to him, move between the present time and 2,000 years in the future. In the future, however, all spiritual realities are visible, including God, Satan, angels, and demons. The only bridge between these two realities is Thomas' blood; using this bridge, several others are able to switch realities.
In both times, the world is on the brink of disaster, thanks to the forces of evil. However, the situation is more dire in the future. Those faithful to God, a number which represents the church, are arguing amongst themselves, despairing of God's very existence, and lusting for battle with the forces of evil, namely the Horde. In these stories, the reality of sin is represented by a skin disease similar to scabies. The faithful are cured of this by diving into their holy pools, which represents coming to faith in Christ. There are also half-breeds--those who are not Horde, who believe in God, but have not believed in Christ. The half-breeds and the believers join together to battle the Horde, in the ultimate showdown between good and evil, which also includes angels and devils. As the battle comes to a head, the arrogance of evil is evident, but they are proven wrong and defeated. The book ends with what is the beginning of the series, the beginning of the book Black.
This is a wonderful book, a very clear parable/fantasy world which illustrates the true end of all things, as predicted by the Bible. Anyone who enjoyed the Narnia Chronicles would appreciate this entire series greatly.