Well, if you'd want to make a book public, on instruction and stuff, it would be useful, and the fact you can have a sign that will let you read it is even more useful.
For example, people make exp farms, and tend to have a small room cramped with signs, that are really not pleasent to read, and sometimes the farm owner need to repeat them and re-re-explain, since the signs aren't that fulfilling, but it the owner were to have a magical way to let his customers read the full instructions while he's not on, maybe it'd save him lots of time.
Or for another example, making a free for all magazine, and instead of making loads of copies, just one sign for people to check out when they do, or it could be used as a list of prices in a shop.
What about adventures, and parkours? wouldn't it be better to have the story-line in a book form rather than tons of signs that probably people will skip after a while?
Also, things like tutorials usually have a chamber full of signs! why not one click that let's you see it better all concentrated in one place?
P.S-Cats, here is the other part of my essay, xoxoxo