Lectern/BE


 * Block entity data
 * : The book item, without the slot tag, currently on the lectern, may not exist.
 * : The page the book is currently on, starting from 0, does not exist if there's no book. If higher than the total amount of pages in the book, gets set to -1.
 * : The page the book is currently on, starting from 0, does not exist if there's no book. If higher than the total amount of pages in the book, gets set to -1.
 * : The page the book is currently on, starting from 0, does not exist if there's no book. If higher than the total amount of pages in the book, gets set to -1.