It requires only a very short program to print out all possible books, and a much longer program to print out one particular book.
To look at it another way, by the trivial isomorphism between any class and its complement, the library containing all possible books has just as much information as the library containing no books.
A better way of stating this would be to look at how much information you can extract from the library with one book in a given time, as compared to the library that contains "all" books: nearly all such books would have gibberish in them.
Eliezer's statement would be a lot less surprising with a proper definition of "all" :)
