A XVIth Century book held in the National Library of Sweden's collection features a "sixfold dos-a-dos binding," meaning that the book could be opened in six different ways to reveal six different texts ("devotional texts printed in Germany during the 1550s and 1570s,including Martin Luther, Der kleine Catechismus"), with the hinges doubling as latches.
You may remember a blog I posted about dos-à-dos (or "back-to-back") books. These are very special objects consisting of usually two books, which were bound together at their, well, backs. When you were done with the one book, you would flip the object and read the other. The dos-à-dos book you see here is even more special.
(via Open Culture)