By saying that the person who reads this book is blessed, John is saying that the reader is much more than happy, but he is favored by God. As the verse continues, we read that "the time is near." This is a reference to Christ's return and the judgment that will come with it. This is a theme that is echoed by almost all of the New Testament, as in James 5:9, which says, " The Judge is standing at the door!".
Revelation 1:4 provides yet another intriguing aspect of the book in general. "John, to the seven churches in the province of Asia from the seven spirits before his throne." This demonstrates one of the distinctive features of Revelation, the repetitive use of the number seven. In totality, it is used 52 times throughout the entire book. There are seven churches (1:4), seven spirits (1:4), seven golden lampstands (1:12), seven stars (1:16), and many others. .
Verse 1:7 produces a bit of a conundrum. It states, "all the peoples of the earth will mourn because of him." Jesus is of course the "him" being referred to here. However, the problem at first glance is that all people "will mourn." Christians believe that Christ's second coming will be a time of great celebration and a time eagerly awaited. Yet this verse says that it will be a time of mourning. Upon closer inspection however, and good cross-referencing, we find that it does not mean we will mourn him coming. Instead, it can mean one of two things. First of all, it could mean that all humanity will mourn what was done to Jesus on the cross. Secondly, there could be a limitation on "all." In Revelation 13:8 it says, "And all that dwell upon the earth shall worship him, whose names are not written in the book of life." This states that all means all who are not saved. This could also be what 1:7 means when it says all, instead of meaning all people on earth.
Eventually, we come to find out how John had this revelation.