Algorithms should inform book culling decisions made by the Librarian, but they shouldn't replace the Librarian's knowledge and expertise.
How can circulation numbers take into account people who aren't using the library because it already doesn't have anything they want? I can't be alone in this, but simply looking at circulation numbers won't capture that, and piloting with a book or two from those categories won't get me back in (I probably won't notice because, after many disappointments, I've mostly stopped looking). Let an algorithm go nuts on that data without human judgement and I suspect you'll gradually put more and more people in my position, unless it's a damned smart one.
1. Regular strategic planning which includes a community survey. This is conducted by an outside firm and non-users are targeted as part of the survey. We also do focus groups.
2. Interlibrary loan. You local library can likely get titles from other libraries. This should inform the collection.
3. Patron driven acquisition. Some way of suggesting books should be available. We buy most suggestions and find that books that are suggested circ better than ones selected by staff (generally, anyway).
I disagree. A book might go out once and chance someone's life. Another might go out a hundred times and sit unread, or have a negligible impact. An algorithm can't determine this. A good librarian can.
LOL no, by that logic The da Vinci Code or Harry Potter books would be literary landmarks. Now, I enjoy a good yarn as much as anyone (and Dan Brown and JK Rowling write great yarns) but it's not like books and the book selling industry are all a giant intellectual meritocracy, marketing and commercial leverage have a lot to do with it. Certainly popularity is a useful signal, but things can be popular because they appeal to a lowest common denominator rather than because they're of great quality.
Let's take JK Rowling's Harry Potter works as an example. They're excellently crafted in terms of narrative pacing, clear characterization, and engaging storytelling. I enjoyed them hugely when I read them a few years ago, and happily spent a week or 10 days immersed in the wizarding world. Anyone who likes reading can enjoy them, and aspiring writers can learn plenty from studying them. At the same time, they're very formulaic and recycle lots of common fictional tropes --- indeed that's partly why they're worthy of study, - their very shallowness makes it easier to spot the structural features. But we would be making a mistake is took the excellent qualities as the standard of value, because the popularity of Harry Potter and its many imitators in the marketplace would have a tendency to crowd out books that excel in other areas where works of popular fiction are deficient.
It's fine for publishers and bookstores to pursue the public taste wherever it leads, but the function of the library is provide more rounded and balanced offerings whose value will span generations rather than only focusing on what's most popular. There's a lovely little library a few blocks from me that I thought I would spend one day a week in when I first saw it, but I hardly ever go there because the selection is abysmal. It's full of multiple copies of things that used to be popular, and woefully lacking in good things that were never very popular. A library's primary purpose is to be full of good books so that even if you can't find a particular work you hoped to read today (perish the thought that one might have to wait for anything...), you will have many high quality alternatives.
This is only possible of you allow librarians to do their job as curators. They should not be required to distil years of complex and highly individual literary and organizational knowledge into the sort of simplistic metrics that appeal to professional administrators. Of course, part of the problem is that some people see the intellectual and cultural diversity of libraries as a cultural threat that has the potential to undermine the status quo, and thus attack the function and independence of publicly-funded libraries in an effort to curtail rather than curate the spread of knowledge.