The real problem stems from the fact that Walt Disney started a practice of lobbying to extend copy rights more and more. Now the whole of the entertainment industry is locked so deeply into it. Also since so many go by the copyright laws of the US, then content creators and Intellectual Property owners sit on a very narrow edge concerning how their content. If they allowed this they can actually lose all claim to the content under the law, this is the same reason some authors have issues with fan fiction. Basically copyright laws as they stand are a complete ass backward mess, and they're designed that way not to protect actual I.P. creators, the artists they employ, or they paying customer. They're designed specifically so that publishers retain control of creative works so they can line their greedy pockets. When it comes to Music, Movies, and Video Games.
Luckily it seems that book authors have been able to avoid this. Still the open domain ceased to exist sometime around when Walt Disney was about to loose Mickey to open domain. Which is a crying shame and the reason it's impossible to get of books like Leslie Charter's "The Saint" series. His copy rights survived past the Mickey Mouse protections, so if none of his heirs want to print it, it stays indefinitely out of print. Thankfully things that had their copyrights expire prior did go into the open domain, but it's a sad state for any thing that got renewed, even after the author died.
Luckily it seems that book authors have been able to avoid this. Still the open domain ceased to exist sometime around when Walt Disney was about to loose Mickey to open domain. Which is a crying shame and the reason it's impossible to get of books like Leslie Charter's "The Saint" series. His copy rights survived past the Mickey Mouse protections, so if none of his heirs want to print it, it stays indefinitely out of print. Thankfully things that had their copyrights expire prior did go into the open domain, but it's a sad state for any thing that got renewed, even after the author died.