Charles Ellicott Commentary Jeremiah 51:60

"And Jeremiah wrote in a book all the evil that should come upon Babylon, even all these words that are written concerning Babylon." — Jeremiah 51:60 (ASV)

So Jeremiah wrote in a book. —The “book” is, as elsewhere, a parchment roll. Stress is laid on the fact that the long prophecy was all written on one roll, so that it might be a more fitting symbol of the city that was its subject.