The first five verses of the Book of Revelation (prologue) contain a number of important details.  They tells us of Who is the Subject (Source) of the book, the scribe of the book, and about the specialness of the book and include the salutation of the book. 

If we ever are prone to question the fantastic predictions of Revelation, we need only remind ourselves of God's flawless track record.  There have been hundreds of Bible prophecies literally and meticulously fulfilled in the past, many of which (like Revelation) were long-range prophecies scheduled for fulfillment in the far distant future, making them beyond the ability of either angel or man to predict - either by guessing or analytical reasoning.  Just like all the previously fulfilled prophecies of God, those found in Revelation will likewise come to pass!  Since every person alive today will be a participant in at least some of the events described in this book, it is vital to understand them (i.e. Rapture, Tribulation, Marriage Supper of the Lamb, Millennial Kingdom, Great White Throne Judgment, New Heaven and New Earth, etc.) to rightly prepare for them - or (in some cases) to avoid them!