The notion of the “adoption of sons of God” is a fundamental concept in biblical theology, particularly in the New Testament. In ancient Roman culture, adoption was a common practice. But what's really interesting is how the Apostle Paul uses this concept of adoption to describe our spiritual relationship with God.
God initially created man as a mere animal, but later upgraded man to a spiritual being by breathing into man His Holy Spirit. Man became a living soul, a son of God. The implication of being a living soul is that man could grow in divinity towards the spiritual level of God, just like a natural child grows towards the level of his /her parent. This potential that God created into man did not go down well with God's angels, as they feared that man could rise above their spiritual level. One third of god's angels rebelled against God for this reason. The leader of the rebellious angels, now known as Satan, immediately went to Garden of Eden where man was and made man to stop being a living soul--the Fall of man. Man became a dead soul.
In order to restore mankind to being living souls, God set into motion a process to adopt sinful human beings as His sons. To this end, brought Jesus Christ into the world to pay the price for the adoption of mankind as sons of God and to establish the Church as a medium to transform sinful human beings into proper members of God's holy household. The price that Jesus Christ paid is to offer himself as a sacrifice of atonement for the sins of mankind. According to Re. 5:9, with his blood Jesus Christ purchased men for God.
Jesus Christ established the Church as a platform on which mankind could be born again, in water and in the Spirit, and on which mankind could learn to grow in divinity towards the level of God. It is this growth in divinity that ultimately qualifies a human being to be adopted as a son of God.
The key to growing in divinity is to always abide in Christ. Christ actually means “the anointing” or the Holy Spirit. Anyone who is born again is in Christ, which simply means that the Holy Spirit dwells in the person. Ep. 4:30 warns against grieving the Holy Spirit, which will make the Holy Spirit to go out of a person. That was what happened to Adam and Eve in the Garden of God. They turned away from God's word and thereby grieved the Holy Spirit that was in them; the Holy Spirit moved out of them and sin went in. The key to abiding in Christ to constantly hold on to words of God. All these are explained in this book.
In Re. 3:10, the Lord Jesus Christ talks about a great worldwide trial. This trial will happen during the end times, very close to the time for adoption of sons of God through resurrection. This great trial will be accessioned by the hurling into the world all the demons in the universe (Re. 12:7–9). Satan and his demons will make a very great effort to prevent human beings from growing in divinity and thereby be adopted as sons of God. There will be indescribable level of evil on earth, as demons roam about in the world. Even some most highly regarded Christians will fall away from faith in Jesus Christ. In Re. 3:11, Jesus Christ warns that we should not allow anyone to take our crowns. The book covers how to prepare to overcome during the great worldwide trial. The great worldwide trial is the qualifying examination for adoption of sons of God.
Finally, the book throws some light on the 144,000 Israelites. The 144,000 Israelites are end-time evangelists whose purpose is to make the Church holy and blameless. They together form the woman of Revelation 12. They will give birth to the perfect Church (the manchild of Re. 12:5).