MoM: you're right. The chains were attached to the front edge of the cover at the bottom. If the books were put in page-edge first, the chain would get caught under the book and ruin it. So the books were put in spine first. Also, at that time, a book's title was not written on the spine so it didnt matter.
I thought that would have been harder to solve.
Yes, I got this info from "The Book on the Book Shelf," by Henry Petroski.
Thanks for the reference, MoM. I will definitely check it out.