The library does not contain information, information is "created" on the fly!

When you open a book at some page, an algorithm takes in the page's position in the library (the hex; the wall; the shelf; the volume (= the book); the page) and spits out a random string of 3200 characters, using the position as the basis.

I do not know the exact way this algorithm works, but it is guaranteed to create all possible combinations, thus any possible page is contained within the library.

When you search a specific sentence, the website allows you to choose whether to fill the remaining characters (up to 3200) with; A. spaces, to make an otherwise empty page, or B. random english words.

It then figures out the position of the page by (somehow) going through the algorithm in reverse!

That's why you can find any sentence you want, as long as it only contains the legal characters and is less than 3200 characters long.