The first thing most people see of a book is the cover, and despite old adages, most people will judge the quality of the book by it's cover. In the case of early printed books, covers were often the most beautiful part of the book.
Covers in the fifteenth century were often made out of wooden boards covered partially or in full with leather. The leather was often tooled, either by hand or using a tool press. Occasionally, as in the case of the Al-Bukhari or Pfintzing, color or gilt were added to the cover to highlight the chosen design.
Sometimes, the leatherworker creating a cover treated the leather with special chemicals to create a particular color or design on the leather. Looking closely at the Durande, an amorphous tree shape becomes visible in the coloration of the leather, which is a common treatment design. The appearance of the leather of the Pfintzing is also chemically created.
Tooled designs varied by artist, but floral and historical designs were common. A wealthy individual might commission a family crest tooled into the cover of their books.
In the sixteenth century, a move began toward the use of pasteboard instead of wood for the boards under the leather covers. Pasteboard, consisting of multiple layers of paper glued together and laminated, was a cheaper alternative to wood. This was one more step in the process of books becoming more accessible to all people.
Rarely, wood or pasteboard books were covered in part or in full with manuscript remnants instead of leather. In the case of the Prologus in Bibliam, the hand drawn musical score on the cover reflects the religious nature of the text.
Throughout this time period, an economical alternative to the leather bound hardcover book was a soft bound book with a parchment covered paper wrapper. The bands of the binding were most often affixed between the end papers and the parchment cover, although sometimes the bands would be pulled all the way through the cover to be visible on the outside of the book. Although not as durable or aesthetically pleasing as a hardcover binding, many early printed books have survived in good condition with their original parchment wrappers.