There is zero IC reason why we shouldn't be able to buy a blank book and write in it. The main benefit would be a much higher character limit, the drawback would be it would weigh one pound instead of zero. There is also no IC reason why you shouldn't be able to copy out, by hand, any book you find. It would take ages of boring, tedious work in-game to do it, but hey, if you want to, you should be able to. Sure, there's the risk that people will plagiarize other's work, but the highest social level we have is Dementlieu's rennaisance era, which had zero copyright protection, and what, exactly is the worst that will happen? Someone will plagairize and sell someone else's manual to alchemy or something? As has been pointed out, you can already do that with the press.
Speaking as someone who's old character was charged with trying to sell another character's book on herbalism (with permission), I can tell you that such things are not big money-makers.