I always said that books became longer when we switched from typewriter to word processor because when you made an insertion on a word processor you no longer had to retype the page (and potentially all the pages following the insertion point).

What was the first book typed? Mark Twain’s Life on the Mississippi is the winner Page Turner tells us in a tweet, and directs us to Slate’s article on the first one written on a word processor.

I wonder if typescript tended to increase the length of books in its day — after all retyping (or paying someone to retype) your book has to be easier than rewriting it by hand. But of course that’s not what you’d do — we have all seen manuscript pages from Dickens, Tolstoy,Christmas-Carol RIA10-638559

and whomever where one is amazed the compositor could work through the deletions, insertions, and transpositions. I suppose the urge to have a neat, clean typescript really only came about when the technology to enable that (i.e. the typewriter) became available. Though perhaps a less successful author than Dickens would have been expected back then to turn in a clean manuscript.