I went to check and it seems like it works fine for plenty of other public domain books. The picture of Dorian Grey, Pride and prejudice and what have you. I can ask for x amount of paragraphs from a specific and such.

I doubt every part of those books get quoted everywhere on a numbered basis like the bible might be. For only recently public domain books it seems to be overly cautious trough the retroactively applied filtering where it refuses if it suspects there might be a single country where copyright still applies.