A neat little book

I recently picked up a neat little book at the local library book sale. It was never part of the library collection; it's a 1923 book called "Representative English Essays". It was obviously meant to be a textbook, and in fact graffiti inside indicates it belonged to a student at Austin College in 1926.

It was cheaply printed. The cover is little more than a particularly heavy stock of cardboard. The thing I found interesting - confusing? - is that in a number of pages were not separated. It's like pages were printed in multiples of four and were meant to be separated when the book was bound and the pages trimmed - and because it was a cheap print job, the trimming was sloppy and a number of pages not cut apart.

I suppose because it WAS a college textbook the owner did not read it, otherwise the pages would have been cut apart. I've kept a small pair of scissors next to it on a table, and every time I find one of these conjoined pages I cut them apart.

It's an excellent book, by the way, coming right at the start of the era when the radio rose up and dominated storytelling. It represents the cream of essays from the era when READING was the dominant form of entertainment for many people. Authors include Alfred Tennyson, Francis Bacon, Edgar Allan Poe, Thomas Carlyle, John Ruskin, Richard Steele, William Hazlitt, William Makepeace Thackeray, George Henry Lewes, Henry Seidel Canby, Henry Thoreau, William Beebe, Lafcadio Hearn, Woodrow Wilson and others.

Does anyone know the printing process that would explain why so many of the pages were never cut apart?