It is one of the more peculiar aspects of scholarly publishing that although everyone expects that academic books will find a place in libraries, no one knows how many books actually get there. This doesn’t mean that every scholarly book can be found in every library; far from it. Nor does it mean that the books found in libraries are in great demand (the common estimate is that 40% of all books in academic libraries never circulate, but I would like to see more evidence of this). The problem is simply that when a book is published, it is sent into the marketplace where a host of intermediaries move it along until it gets to the ultimate user. Those intermediaries may or may not let publishers know where the books end up. I am reminded of Longfellow:
I shot an arrow into the air,
It fell to earth, I knew not where.