One possible reason it might have seemed slightly more useful in its time is that many books much bigger than what we expect today. I've seen some books from th

One possible reason it might have seemed slightly more useful in its time is that many books much bigger than what we expect today. I've seen some books from the 13th century that are over 20 inches across when open and quite heavy and I don't think those books were particularly large. (Codex Gigas is over 40 inches across when opened and weights 150 pounds, but is probably the largest book we know of.) Having 8 books of 24 inches across open next to each other would take 16 feet or so of linear space. In the drawings it doesn't look big enough to handle these large books unless it was made slightly wider. Of course your objections are probably very much why it was never built until now. :)