Books that are bound with wire (or staples) generally have the lowest binding cost per book. Books with the wire binding are said to be stitched. A book with stitching through it's spine is called saddle stitched after the saddle it sits on as the wire is stitched through the spine. Most thin booklets and catalogs are bound this way.
While it doesn’t accommodate large page counts or thick bulks, it allows the pages to lay fairly flat. Books that are meant for children (like coloring books) were frequently saddle stitched, but possibility of injury from the wire has persuaded most publishers to bind children’s books with glue.
Early soft cover books frequently bound the pages with a wire roughly 3/8” in from the bind at both the head and foot that traveled through the entire book. The cover was applied to the spine with glue. Such books were called “side stitched” or “side wired” and were incredibly durable. If type in the text got to close to the bind margin it was difficult to read, but with a little forethought an indestructible directory could be easily constructed.