Answer:
John (the Beloved) ate the book.
Revelation 10:10 And I took the little book out of the angel’s hand, and ate it up; and it was in my mouth sweet as honey: and as soon as I had eaten it, my belly was bitter.
Ezekiel was also told to eat a book (or scroll):
Ezekiel 3:1-3 Moreover he said unto me, Son of man, eat that thou findest; eat this roll, and go speak unto the house of Israel. So I opened my mouth, and he caused me to eat that roll. And he said unto me, Son of man, cause thy belly to eat, and fill thy bowels with this roll that I give thee. Then did I eat it; and it was in my mouth as honey for sweetness.
Good question,
Pastor Brad