Christ is the Mighty Angel.

The little book in His hand is the same book
that He had in Chapter 5.

In that chapter, a sealed book is handed to
Christ. He was the only one found worthy
to open it. He looses the seals so the book
can be opened.

When Christ, in Revelation 10, is seen, all
the seals have been loosed. He has a book
that is now open. This has to be the same
book.