The Book of Revelation to St. John the Divine is a later title.  The original title was likely "The Revelation of God to Jesus Christ."  (Chapter 1:1).  The book opens with the vision of what must "shortly come to pass" but later in Chapter 4 the vision shift to future events.  The 7 Churches to whom the revelation is metaphorically addressed are representative of all Christian churches, but were under Emperor Nero, subjected to intense persecution from without (Nero blamed the 64 AD fire in Rome on the Christians and had many dipped in tar, crucified, and burned in oil, lighting the roads in places in the Roman Empire).  Trouble from within the Churches included Nicolations (followers of one Nicholas, who believed in wife swapping; and, the influence of false apostles.  Chapter 2 points out these problems and gives comfort.