Books and boxes were found in close proximity; before bookshelves, chests were the most obvious place to store books, and the physical features of a bound book often made it visually analogous to a box. The material and tactile connections between book and box play into common metaphors of the book as a receptacle for textual riches, and the chapter brings together responses to the book as box-like object from Erasmus to early seventeenth-century English Protestants, from humanist treatises to portraits. In considering literary and visual encounters with the codex, discussion focuses on the significance of external surfaces, such as gold, blackness, and embroidery, in the fashioning of these inherently box-like objects. While reformers insisted on the Word of God as the only vehicle of truth, they could not escape the fact that it had to be contained in books, unavoidably material receptacles with insides and outsides that could shape and inscribe each other. Protestants remained sensitive to the metaphorical potential of an object with insides and outsides, and this chapter demonstrates that the identity of the ‘book’ was more complex than 'sola scriptura' suggested.