Frankly Speaking: A Brief History of the Short Run

Digital printing has saved the book industry. The old business model that printed an excess of books has been replaced for many titles by a more efficient on-demand model. Consider my personal example: Back in 1972, I wanted to self-publish a book. I only wanted 500 copies, but the printer said the minimum run was 5,000. I still have 4,000 copies in the warehouse, because someone may want a book on 1970s phototypesetting some day.
In 1976-1978 the IBM 3800 roll-fed and Xerox 9700 sheet-fed digital printers introduced a new approach to printing. But the infrastructure for accepting files, electronically collating pages and binding one book at a time was not available. It was 1990 before the Xerox DocuTech was able to produce one bound book at a time, and the late '90s before color-bound books were produced in the same manner.
Not long ago I visited ColorCentric Corp. in Rochester, N.Y., which is like Disneyland for on-demand book printing. Almost every model of digital printer was there and most were popping out one book at a time. The enablers that made this possible are front-end software that routes book files to printers and in-line book finishing.
HP sent me a sample book printed on their roll-fed T-series inkjet printer by Courier Corp. in Massachusetts. It was full color on glossy stock. The run was probably a hundred or so—what I would call a "longer short run."
King Printing in Lowell, Mass., was among the first to apply roll-fed digital book printing with the Screen Truepress Jet. They now have a contingent of presses from Kodak and HP. I should mention that Lightning Source in Tennessee was a pioneer in on-demand books.
Most backlist titles are now printed on-demand and over time; most of the books ordered online might be printed just for the buyer. But some books that sell well will require longer runs. Depending on the quantity, they could be produced via offset. A plant in Chennai, India, produces a few hundred books at a time on small offset presses for UK university publishers. Singapore was once the book-printing capital of the world, but that mantle now goes to China.