I could imagine machine printing of dust jackets lead to the opposite convention. If you are printing a dust jacket, the back of the book is on the left, the fr

I could imagine machine printing of dust jackets lead to the opposite convention. If you are printing a dust jacket, the back of the book is on the left, the front is on the right, and the title is in the middle. Despite reading order being from left to right, people tend to both proof and layout the most 'important' information first. This would be the title page. Once you've laid of the title, the next thing you are going to move to is the spine. A title printed on a book spine from top-to-bottom would be completely upside down from the perspective of the front cover, whereas a title printed from bottom to top would only be 90 degrees off from the front cover. Thus the layout and proofing of the spine would be more "natural". I wonder if there was some sort of technology invented between the widespread adoption of the printing press in Europe, and the adoption of the printing press in the colonies that made the bottom to top layout less obvious. Maybe the colonists were too uncultured to use dust jackets. Edit: I just checked, and I was surprised to learn that every single tilted title goes the same way on my books. I have a lot of old books that I bought at used bookstores just because they looked interesting. Regardless of the binding, age, or field the book was published in, if the title is tilted it goes from top-to-bottom. Fascinating. I did discover some of my books were upside down though.