It is clear that Revelation 6 builds on the throne scene of chapter 5. The Lamb takes the book in chapter 5 and begins to break its seals in our passage above. But a question arises: are the seals the content of the book itself? Or do the contents get revealed only when the Lamb breaks all seven seals? Answering this is crucial for anyone who wants to understand the passage.
If the book is a scroll, shaped like a rolling pin, the seals would be placed outside the "book" and would have to be torn away before anyone could read the book. If the book is a codex (like the book you are holding now), with sheets of paper bound together on one side, you could conceivably seal or tape up the book into seven sections that you could free one at a time.
While the Romans invented the codex form around the time of the composition of Revelation, Jews still use the scroll form for their Bibles up to this day. Christians, however, immediately switched to the new form. Of the hundred or so earliest manuscripts of the New Testament (often existing today only as fragments), only four are in scroll form. We can tell when a manuscript fragment came from a scroll by the slight curvature in the paper that results from being rolled up for a long time.
Why did Christians switch to the codex form for the Bible? Probably because of the four Gospels. Christians wanted to be able to include all four of them in the same document. A scroll that big would be too large to handle, but you could fit all four Gospels into a codex fairly easily. So shortly after the time of Revelation Christians switched to the codex form.
Now back to our original question. Is the book unsealed a scroll or a codex? Are the events of Revelation 6 a view of he content of the book, or are they the kinds of things that lead up to the opening of the book? Fortunately, John does not leave us in any doubt. In Revelation 6:14 he says, "The sky was split open like a scroll being rolled up."
According to this verse the sky opens like a scroll when someone rolls it up. The word for "scroll" in Revelation 6:14 is the same used for the sealed scroll of chapter 5. The sealed scroll, therefore, is clearly not a codex. With a scroll, you would have to break the seals completely before you could read anything inside. Since the author relates the events in Revelation 6 to the breaking of the seals, they do not describe the content of the scroll itself, but are things that have to take place before the scroll can be opened.
Lord, it's great to understand the deep things of Your Word a little better. Help me to trust You even when I don't understand.