The defining feature of the medieval manuscript, the book that was used across Europe before the introduction of printing, is that its contents have been written by hand. A compelling feature of written text from the medieval period is that it produces two kinds of meaning: the meaning of the words themselves, the primary reason for consulting a manuscript, then and now; and more concealed meaning hidden within the shape of the letters. As medieval scribes copied a text, they included information about themselves and their surroundings in their handwriting. How the individual letters were formed depended, for example, on the location and moment of the book’s production, the institution in which the scribe was trained, and even with how much care a text was copied. This is the enigma of the medieval manuscript, that a wealth of historical information is embedded in the appearance of letters – if the code can be deciphered. What methods are available to untangle this enigma? What knowledge hidden in plain sight can be gleaned if we are successful? Why is looking at an old book as useful as reading it?