I love libraries. And I love librarians. They are the most knowledgeable and helpful of people as a class. They seem to get a real kick out of finding stuff for you.
Libraries have the problem of what to do about the increasing numbers of books and journals that they own. This problem is particularly acute for university libraries that do not, as a rule, throw old books and journals away or sell them because they are resources for research that a faculty member or student may need at some point, however rarely. In my own research, I have been very grateful to my university library because it has rare books on obscure topics published over a century ago that I suspect that are almost never checked out. And yet, there they are, just waiting for me.
One solution is to take books and documents that are rarely checked out and send them to an underground storage facility that may be some distance away in some climate controlled environment to prevent deterioration. If a library patron needs such a book, they have to make a request and the book is brought back to the library to check out. The library at Case Western Reserve University uses an outfit known as Iron Mountain for this purpose. It is pretty efficient in that it usually takes just a day or two to get a book from deep storage.
Another solution is to pack the bookshelves more densely. In the CWRU library, the racks of shelves are packed tightly almost touching each other. There is space to walk between them only every ten racks or so. But the racks are on tracks operated electrically and if you want to get between any two of them, you press a button and the shelves move to create a space using up other open spaces to do so. This system too works pretty well. (When it was first set up, my thought was that it looked like the infamous trash compactor in the first Star Wars film and I wondered if it were possible for someone to get squeezed by racks closing in when they were between them. There are of course sensors to prevent that from happening and no accidents have occurred. Not yet, anyway.)
The system used by North Carolina State University takes this close packing to an even greater extreme, with a machine being used to meet any specific book request. The scale of the whole setup looks like something out of a science-fiction film, with 10,000 bins containing over a million books. Interestingly, the system allows books to be stored anywhere in its vast vaults and not according to the sequence of its classification numbers. This enables denser packing by allowing storing books of similar size together. Its specific location in a particular bin and position within a bin is recorded in a computer.
My first thought was that if a book was accidentally misplaced, it would be impossible to find. Of course, librarians are aware of this problem and have addressed it. It turns out that the machine does not make mistakes and that the library does an audit each year of every book it has to make sure that it is in the recorded location.
Of course, if there is a power outage or the machine breaks down, you are utterly stuck until it is repaired. Another downside to this system is that it loses the element of serendipity. There have been many times when I have looked for a particular book on the shelves by its classification number and come across adjacent books of interest in the same field. That will no longer happen when a machine gets your book for you.
This loss of serendipitous discoveries has already happened with electronic journals. Nowadays one goes straight to the article of interest and downloads it. Not browsing through a physical journal means that one does not stumble upon articles of interest other than the one you were looking for. But the quickness and ease with which one can get a journal article from wherever you are more than compensates for that particular loss. Just recently I needed an article from an old journal that was not in the electronic databases. I had to actually go to the university library, take down a massive old bound journal from the shelves and then take it to the scanner to make a pdf copy and email it to myself. All that took quite a bit of time. Holding an actual bound journal in my hands and flipping the pages seemed so strange, like going back in time.
In the case of machine book retrieval, since you have to physically go to the library to get the book, the advantages to the user of the NCSU system are not clear. If many people are requesting books, this system may take longer than you going to the shelves and finding it yourself. The benefits seem more to the university in its ability to store more books and keep track of them better and that definitely compensates for the extra wait time.