There are things that God can reveal and things He can't reveal. Not because He's unable mind you but because those things which would be revealed would show people what they would do before they actually did them. Again, not that God can't do that but He can't without stepping on the "free will" that He has given man.
The Book of Revelation has in it things that we take for granted because of when it was given to John. But if you had it before Jesus died on the cross or when Daniel was in Babylon that would present problems. When the Jews rejected Jesus as Messiah - as a nation - by saying "crucify Him let his blood be upon us and our children" God did not force them to say that - they said that on their own and of their own free will but if they had seen the Book of Revelation they would have thought that it was their duty to say that and to crucify Him on the cross.
Jesus says in Revelation as by way of introduction . . .
Rev 1:5 And from Jesus Christ, who is the faithful witness, and the first begotten of the dead, and the prince of the kings of the earth. Unto him that loved us, and washed us from our sins in his own blood,
Rev 1:18 I am he that liveth, and was dead; and, behold, I am alive for evermore, Amen; and have the keys of hell and of death.
Thus foretelling of his death, burial and resurection before he was crucified if this Book would have been given before hand.
Also, the fact that, at the end of this Book comes the close of the revealed word of God. The close of the canon of Scripture.
Rev 22:18 For I testify unto every man that heareth the words of the prophecy of this book, If any man shall add unto these things, God shall add unto him the plagues that are written in this book:
Rev 22:19 And if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book.
Which is very important. It shows that no one else can add to the Scriptures no matter how lofty his tale is - such as being given a revelation by an angel with 600 wings or something equally as unbelievable and unprecedented as an angel actually giving an already printed book to a guy who looked through crystals to see him when the scriptures say that the word of God was given by . . .
2Pe 1:21 For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.
Besides having to be Jewish.
Rom 3:1 What advantage then hath the Jew? or what profit is there of circumcision?
Rom 3:2 Much every way: chiefly, because that unto them were committed the oracles of God.
It also lines up with the last Chapter of Isaiah which is a kind of numbering check list as to how many books there are in the Bible - in the Old Testament and the New Testament.