This was a while ago, but I thought around the time of AOS there was a bug that you could drop items into runebooks and spellbooks and you couldn't get them back out. It was a short lived bug (about 2 weeks maybe). It did show the weight and possible item count (can't remember). I had to page a gm to remove a few items and get them back from a spell book.
This could be a book from that time period. However, it is just as likely that it is html or something else.