Throughout the Bible, the phrase "blessed is he," is used often to describe the Believer who lives and abides by God's word.
This can be seen by searching the Bible for this phrase and reading how it is used contextually.
Jesus uses a similar phrase extensively in His Sermon on the Mount – the Beatitudes (Matt 5:1-11).
This may provide some context to the Revelation of Jesus Christ.
Is John using "blessed is he" to place a special emphasis on the book of Revelation? It is not likely that the emphasis is as
a priority of importance over the other books of God's word; but, rather as an emphasis of its urgency "for the time is near."