Peterson is exploring the image of "eating the book" found in Revelation 10, when the angel gives the scroll to the apostle John (who is having his visions on the island of Patmos) and instructs him to eat it. As Peterson writes:
"John started to write down what he was hearing -- he'd never heard a sermon like this one-- but then was told not to. A voice told John to take the book from the huge angel, this God-Messenger preaching from his world-straddling pulpit. And so he did. He walked up to the angel and said, 'Give me the book.' The angel gave it to him, but then said, 'Here it is; eat it...Eat this book.' Don't just take notes on the sermon. Eat the book. And John did it. He put away his notebook and pencil. He ate the book (Rev. 10: 9-10a)...
St. John wasn't the first biblical prophet to eat a book as if it were a peanut butter sandwich. Ezekiel had also been given a book and commanded to eat it (Ezek. 2:8-3:3). Jeremiah also 'ate' God's revelation, his version of the Holy Bible (Jer. 15:16). Ezekiel and Jeremiah, like John, lived in a time in which there was widespread pressure to live by a very different text than the one revealed by God in these Holy Scriptures. The diet of Holy Scripture for all three of them issued in sentences of tensile strength, metaphors of blazing clarity, and a prophetic life of courageous suffering. If we are in danger (which we certainly are) of succumbing to the widespread setting aside of the Holy Scriptures and replacing them with the authoritative text of our own experience -- our needs and wants and feelings -- for authoritative direction in our actual day-by-day living, these three rough-and-tumble prophets -- John, Ezekiel, Jeremiah -- responsible for the spiritual formation of God's people in the worst of times (Babylonian exile and Roman persecution) ought to be able to convince us of their gut-level necessity.
Every word in this book is intended to do something in us, give health and wholeness, vitality and holiness, to our souls and body. That's why the Christian community has expended an enormous amount of energy and intelligence in learning how to 'eat this book...' (pgs. 13, 15-16)
I really found the parallels of our time with the prophets' time (exile) and John's time (persecution) resonant, especially in that danger that Peterson highlights about our tendency to replace the Scriptures with our own selves. I think that is a big part of sinful human nature down through the ages, in all times...to attempt to live outside of the ways God calls us to live. That's part of our bentness. You would think that in times of trouble, we would automatically turn to resources beyond ourselves, especially God-inspired and God-breathed words that have proven to be strong and true and to lead the community of the faithful down the right paths toward Jesus. But we get inverted, we turn inward and try to come up with our own ways and our own paths, which is especially dangerous when we often forget that our "selves" have been deeply formed by something...and if not this book, then by the "book" of the world, the culture all around us.
It was really helpful for me to read his unpacking of the "eating the book" metaphor, here and in other places. There's a tendency (in me, at least) to think that if I assimilate things with my mind and at least on some level with my heart, then I've done the best I can do. What Peterson is talking about here is us assimilating what God has revealed, so fully that it's as though we've ingested it. Note that he doesn't say "every word in this book is intended to do something for us" or even "to" us, but IN US.
How do we do this? How do we read the Word faithfully and truly, and not just read it, but eat it, as though we've sat down to a feast? I need help with this, as we all do (that's one reason we often read it in community) and I need to continually ask God to give me a hunger for this book he wants me to eat.