"Grace and peace to you from him who is and who was and who is to come..." Revelation 1. 4
The Book of Revelation, which draws the whole Bible to its conclusion, has been described as "an apocalyptic prophecy in the form of a circular letter". That is to say that it is about how God will bring history itself to his own appointed conclusion and what will happen on the way, delivered in the form of a letter addressed to a series of churches around an ancient postal route. The naming of these churches at the beginning of Revelation locates the route in Asia Minor (modern Turkey) and the fact that there are seven (the perfect number) suggests that the message of Revelation is intended for everyone.
Needless to say Revelation is not light reading. Perhaps because it was written from exile to those facing persecution, the message is concealed within secret metaphorical code. Presumably it was understood by its original recipients but then much of the detail of its meaning appears to have been lost. Only in recent years have scholars begun to unearth its secrets.
At its heart, Revelation is a message of encouragement to fragile communities of faith, facing enormous odds yet conscious they serve a big God with a glorious future. By way of "food for the journey", consider the following promises the Risen Lord Jesus makes to the churches mentioned, despite their weaknesses and short-comings: "the right to eat from the tree of life" (2.7), "the crown of life" (2.10), "some of the hidden manna... a white stone with a new name" (2.17), "authority over the nations... the morning star" (2.26 & 28), "to be dressed in white... acknowledged before the Father" (3.5), "to be a pillar in the temple... a new name" (3.12), "the right to sit on the throne" (3.21).
Depending on your mood and situation, Revelation will humble you or it will raise you up, perhaps both. Its essential purpose is to acknowledge that what appears weak and of little significance to worldly society, which is dying, has a glorious future in the purposes of God, which have defeated death and are destined for everlasting life.