As I reported earlier, Oxford and Cambridge University Presses have been conducting a survey of monograph use. The results are reported on at The Scholarly Kitchen, where there’s also a link to the principals’ own report on their research. The Foreword to the study explains its genesis in the need to resolve conflicting views of the monograph: “For many years, we’ve heard that the days of the monograph are numbered, that it is inaccessible and old-fashioned, that the world has moved on. And yet, we see ever more monographs submitted to publishers and a growing online usage of monograph materials.”
The outcome, perhaps unsurprisingly, is that monographs remain important in the humanities, less so in the sciences. It was always difficult to get scientists to write books surveying a topic. They tend to be focussed on results which get communicated in journal articles.

From the report
Wulf and Anderson conduct a to-and-fro discussion of the report, leading one of them (Anderson) to speculate whether “perhaps some monographs should be written, but should not be published, or at least not published in the traditional way.” Maybe I am just showing my ignorance, when I react to this by thinking “But isn’t this exactly what has been happening for ever?” Lots of monographs get written but not published: we call them unpublished PhD theses, and a copy of each is deposited in a library where the odd, highly-motivated researcher can track them down and consult them.
The discussants focus on the fact that fewer books are being taken out from our academic libraries: but this doesn’t have to mean that researchers are ignoring books. In the olden days in order to find out what was in a monograph you had to sit down and look through it. Now you can sample it online, and rule it out before you ever have to visit the library and look at the actual object. Doesn’t mean you’re not using the book just as much as you ever did. Doesn’t even have to mean your not using the physical copy as much: it just means you don’t end up taking off the shelves those books you don’t need to take off the shelves.
So we can assume, I guess, that in the face of this research CUP and OUP will be continuing publishing monographs. In a way of course that was never in doubt. As long as people write these things there will be a need to publish some of them. The real problem is how to make them affordable, or at least not utterly unaffordable. The number of copies of a monograph that can be sold has come crashing down. In my youth 2, or 3,000 was not unheard of. Now print runs of 2, or 300 can be met. I. really don’t think this is because “people don’t buy books any more” — I think it’s absolutely because with the subdivision of disciplines into ever more and more specialized streams, there are just fewer researchers involved in each topic, so that the audience is perforce smaller. What this means is that the retail price of the monograph has to go up: those fixed (plant) costs have to be amortized over the quantity sold, and thus price has to give. This all tends to get a bit circular: higher prices mean fewer buyers; fewer buyers mean higher prices. Still at any given time there is a sort of temporary equilibrium.