THE KEY MEANING OF THE BOOK OF REVELATION.

The Book of Revelation occupies a central place in Christian doctrine. Its title is derived from the 1st word of the text, written in Greek, 'apokalypsis,' meaning 'unveiling' or 'revelation.'
The author of Revelation is plainly named 'John.' It begins with John, being a prisoner on the island of Patmos in the Aegean, where  he had been exiled because of his Christian faith. He was well known among the churches of Asia, and was classed as a "prophet." He is being given a series of 4 visions from the Son of God, and addressed a warning letter to the "7 Churches of Asia."
Patmos is seldom mentioned by ancient writers, but very little can be conjecture about the earliest inhabitants. It was believed that Patmos came into existence as an island at the bottom of the sea.
According to a legend in Greek mythology, the island's original name was "Letois," after the goddess and huntress of deer Artemis, daughter of Leto (meaning 'disputed').
Leto was a daughter of the Titans Coeus and Phoebe, the sister of Asteria, and the mother, by Zeus, of Apollo and Artemis. The island Kos is claimed as her birthplace.
In the Olympian scheme, Zeus is the father of her twins, Apollo and Artemis, the Letoides, which Leto conceived after her hidden beauty accidentally caught the eyes  of Zeus. The myth records his pregnancy and her search for a place where she could give birth to her twins, since Hera in her jealousy had caused all lands to shun her.  When Hera, the most conservative of goddesses -for she had the most to lose in changes to the order of nature- discovered that Leto was pregnant and that Zeus was the father, she realized that the offspring would cement the new order. She was powerless to stop the flow of events. Finally, Leto finds an island that is not attached to the ocean floor so it is not considered land and she can give birth. Once the twins grew up, Leto withdrew, to remain a dim.
Artemis frequently paid visits to Caria, the mainland across the shore from Patmos. There she met the moon goddess Selene, who cast her light on the ocean, revealing the sunken island. Selene was always trying to bring the sunken island to the surface and hence to life.  Selene finally convinced Artemis, who, in turn, gained her brother Apollo's help to persuade Zeus to allow the island to arise from the sea. Zeus agreed, and the island emerged from water. The sun dried up the land and brought life to it. Gradually, inhabitants from the surrounded areas, including Mount Latmos, settled on the island and named it "Letois" in honor of Artemis.
In the Classical period, the inhabitants preferred to identified themselves as Dorians descending from the families of Argos, Sparta, and Epidaurus, further mingling with people of Ionian ancestry. During the 3rd century BC, in the Hellenistic period (between the death of Alexander the Great in 323BC and emergence of Roman Empire), Patmos acquired the form of an acropolis (core built upon a hill with precipitous sides) with an improved defense through a fortification wall and towers.
Early Christian life on Patmos barely survived. Muslims raided the area from the 7th to 9th century. Then the island was controlled by the Ottomans for many years. In 1912, in connection with Italo-Turkish War, the Italians occupied all the islands of the Dodecanese, including Patmos. The Italians remained there until 1943, when Nazi Germany took over the island. In 1945, the Germans left and the island of Patmos remained autonomous until 1948, when it, together with the rest of the Dodecanese Islands, joined the independent Greece.
The Dodecanese (12 islands) are a group of 15 larger plus 150 smaller Greek islands in the Southern Aegean Sea, off the coast of Asia Minor (Turkey), of which 26 are inhabited. They have a rich history, and many of even the smallest ones boast dozens of Byzantine churches and medieval castles.
The most historically important and well-known is Rhodes, which has been the area's dominant island since Antiquity. Of the others, Kos and Patmos are historically the more important.
The name "Dodecanese" were applied to the 12 Cyclades islands clustered around Delos. The Cyclade culture is best known for its schematic, flat idols carved out of the island's pure white marbles centuries before the Minoan civilization arose in Crete. A distinctive culture amalgamating arose between Anatolian and mainland Greek elements in the Western Aegean before 4000 BC. The islands faded into insignificance, with the exception of Delos, which retained its archaic reputation as a sanctuary throughout antiquity and until the emergence of Christianity.
Delos has a position as a holy sanctuary for a millennium before the Olympian Greek mythology made it the birthplace of Apollo and Artemis. From its sacred harbour, the horizon shows the 2 conical mounds that have identified sacred landscapes, one, retaining its Pre-Greek name Mount Kynthos, is crowned with a sanctuary of Zeus. Established as a cultural center, Delos had an importance that its natural resources could never have offered. In this vein Leto, searching for a birth-place for Artemis and Apollo, addressed the island:
  "Delos, if you would be willing  to be the abode of my son Phoebus Apollo and make him a rich temple; for no other will touch you, as you will find: and I think you will never be rich in oxen and sheep, nor bear vintage nor yet produce plants abundantly. But if you have the temple of far-shooting Apollo, all men will bring you hecatombs (a sacrifice to the gods of 100 cattle) and gather here, and incessant savour of rich sacrifice will always arise, and you will feed those who dwell in you from the hand of strangers; for truly your own soil is not rich."
A hecatomb was a sacrifice to the gods of 100 cattle. Hecatombs were offered to Greek gods Apollo, Athena, and Hera, during special religious ceremonies. At the end of the Olympic Games, a hecatomb was also offered to Zeus at Olympia. In the Illiad the religious sacrifice is described as follows:
 "They ranged the holy hecatomb all orderly round the altar of the god. They washed their hands and took up the barley-meal to sprinkle over the victims, while the priest lifted up his hands and prayed aloud on their behalf. When they had done praying and sprinkling the barley-meal, they drew back the heads of the victims and killed and flayed (skin is removed from the body) them. They cut out the thigh-bones, wrapped them round in 2 layers of fat, set some pieces of raw meat on the top of them, and then the priest laid them on the wood fire and poured wine over them, while the young men stood near him with 5-pronged spits in their hands. When the thigh-bones were burned and they had tasted the inward meats, they cut the rest up small, put the pieces upon the spits, roasted them till they were done, and drew them off. Then when they had finished their work and the feast was ready, they ate it, and every man had his full share, so that all were satisfied. As soon as they had enough to eat and drink, pages filled the mixing-bowl with wine and water and handed it round, after giving every man his drink-offering. Thus all day long the young men worshipped the god with song, hymning him and chanting the joyous paean, and the god took pleasure in their voices."
The predominant view of the Book of Revelation alludes to the ancient way of life. The Book rarely quotes directly from the Old Testament, but every verse alludes to or echoes the Older Scriptures. Over half of the references stem from Daniel, Ezekiel, Psalms, and Isaiah, with Daniel providing the largest number in proportion to length and Ezekiel standing out as the most influential. The allusions clearly show in a symbolic way the behavior of the ancient elemental spirits that existed in heaven before the world came into existence and then when the earth was formed.
The main purpose of the Book is to reveal the divine person of the Son of God as the Redeemer of the World and as the conqueror of evil, presenting in symbolic form the plan by which He will carry out His work.
The structure of the plan is built on 4 great visions, each of which begins with the phrase "In the Spirit," and contains one aspect of the spiritual person of Christ in His capacity as the Judge of the World.
The letters addressed by the Lord to the 7 churches are typical of the churches of all time. In them He voices His commendations and criticism, concluding with a warning and a promise.
Beginning with the 4th chapter, the seer is transferred to heaven, and beholds "things which must be hereafter." Through a succession of judgments, the seals, the trumpets, and the bowls, the earth is punished for its sin, and the great Day of God's wrath is ushered in. No indication is given of the length of the process, though it seems to accelerate toward the end.
In the 17th chapter through the 20th, we are given a detailed view of the consummation of the age. The return of the Son of God in glory with the armies of heaven, the establishment of the Kingdom and its conclusion in the final judgment of the white throne, and the creation of the new world are depicted.
The last vision continues the third vision by describing more fully the nature of the City of God.
The conclusion of the Book is a call to 'devotion.' If the Son of God is going to return, holiness and industry are obligatory upon His people.