Many translations of the Bible suggest that the scroll is in the right hand of the One sitting on the throne. But recent research suggests that the phrase "in the right hand" probably means "at the right side" instead. This makes a lot of sense in the light of how the ancient world used thrones. People in those days generally felt that the right side of the king was the highest possible place of honor. Psalms 80:17 and 110:1 describe the king of Israel as sitting at God's right side, and he and God are corulers of the nation.
Many ancient thrones were large enough for three to four people to sit on. It has been suggested that the ancient reader may have understood the scroll to be lying on the throne of God's right side. If that is so, to take up the book is to sit on the throne at God's right side. In other words, when Jesus picks up the book with His hands, He also sits down at the right side of the Father, assuming His role as the new king in the line of David (Rev. 5:5).
In Old Testament times the Israelites had an extended period in which they had no king except God. The country had no clear central control. While putting a king on the throne could cause them to look away from God, in practice things were rather chaotic without an earthly ruler to give direction (Judges 17:6; 21:25). So God permitted them to institute a monarchy, first in the person of Saul (from the tribe of Benjamin) and then with David (from the tribe of Judah). David's reign was so blessed in comparison with Saul's that his reign, and the reign of his son Solomon, became models of ideal rulership for Israel.
So this concept of Davidic kingship lies behind the story of Revelation 5. The Lamb is "the Lion of Judah" and the "Root of David." Elsewhere in the New Testament Jesus sits down at the right hand of His Father on the throne in heaven (Matt. 26:24; Heb. 8:1, etc.). So when Jesus comes and picks up the scroll, He is taking His seat on the throne in the heavenly sanctuary.
Lord, this is wonderful news. The One in charge of earth and heaven is the Lamb that was slain. He knows what my life is like and has felt what I feel. I can trust Him to rule wisely, fairly, and compassionately.