Unfortunately, the King of Misthalin is actually an aspect of the same god who is disguised as Reldo, and therefore the book is actually banned in all of Misthalin, and frowned upon more than being Zamorakian.
Fortunately Zamorak is red and red is power,:that book is red, which again is power - The book has and still is passing through more hands than the destruction of Lumbridge.
Unfortunately, Saradomin owns Lumbridge after what happened back then, and so he takes the book to court, where Saradomin wins and is therefore able to legally destroy all copies of the book...
Unfortunately, regardless of their continued circulation, possession of such a book is now recognised as the most heinous crime, slightly surpassing even Zamorakianism.
Half the people in Varrock were already sacrificed to Saradomin's angry beard.