"In the past teachers have declared Daniel and the Revelation to be sealed books, and the people have turned from them. The veil whose apparent mystery has kept many from lifting it, God’s own hand has withdrawn from these portions of His Word. The very name “Revelation” contradicts the statement that it is a sealed book. Revelation means that something of importance is revealed. The truths of this book are addressed to those living in these last days. We are standing with the veil removed in the holy place of sacred things. We are not to stand without, we are to enter; not with careless, irreverent thoughts, not with impetuous footsteps, but with reverence and godly fear. We are nearing the time when the prophecies of the book of Revelation are to be fulfilled.
"This book opens with the words, “The Revelation of Jesus Christ, which God gave unto Him, to show unto His servants things which must shortly come to pass; and He sent and signified it by His angel unto His servant John; who bare record of the word of God, and of the testimony of Jesus Christ, and of all things that he saw. Blessed is he that readeth, and they that hear the words of this prophecy, and keep those things which are written therein; for the time is at hand.”
"This book demands close, prayerful study, lest it be interpreted according to the ideas of men, and false construction be given to the sacred word of the Lord, which in its symbols and figures means so much to us. There is so much that we positively must understand in order that we may shape our course of action so that we shall not receive the plagues which are coming upon the world. In the Revelation the deep things of God are portrayed. Those whose hearts are wholly sanctified to God will be brought nigh to see priceless gems through the telescope of faith. And as they apply the truth to practice, the still deeper mysteries are stamped on the soul. Those thus honored are to communicate to others that which they have received. And as they do this, angels make the impression on hearts. ...
"Let none think, because they cannot explain the meaning of every symbol in the Revelation, that it is of no use for them to search this book with deep, earnest longing and intense desire to know the meaning of the truth it contains. The One who revealed these mysteries to John can and will give the diligent searcher for truth a foretaste of heavenly things, hereafter to be realized. Rich blessings will come to him who reads and hears the words of this prophecy, and keeps those things which are written therein.
"We have the commandments of God and the testimony of Jesus Christ, which is the Spirit of prophecy. Priceless gems are to be found in the Word of God. Those who search this Word should keep the mind clear. Never should they indulge perverted appetite in eating and drinking. If they do this, the brain will be confused; they will be unable to bear the strain of digging deep to find out the meaning of those things which relate to the closing scenes of this earth’s history.
"When the books of Daniel and Revelation are better understood, believers will have an entirely different religious experience. They will be given such glimpses of the open gates of heaven that heart and mind will be impressed in regard to the character all must develop in order to realize the blessedness which is to be the reward of the pure in heart. The Lord will bless all who will seek humbly and meekly to understand that which is revealed in the Revelation. This book contains so much that is large with immortality and full of glory that all who read and search it earnestly receive the blessing to those 'that hear the words of this prophecy, and keep those things which are written therein.' "
This quote is taken from a letter written January 27, 1900 to F. E. Belden. Read the full passage in Manuscript Releases, volume 18, pp. 22-24: https://egwwritings.org/?ref=18MR.22.