That's a very interesting approach to books. Unfortunately, most suggestions imply that most of the 'action' would either occur from UI-play or be a central part of the game. I'm mostly looking for tools that have a direct effect on gameplay such as 'press A, slash your sword' kind of interaction.
If I'm to include books at all, I need to have 3 solid standalone actions when pressing a key.
1 - Would be a nice way to explain inventory as a whole, but it's mostly just theme-related, not an actual gameplay role per se.
2 - Not bad, but it comes with a system, I'm actually trying to keep things simple. The focus is really on the tools you gather and what they can do.
3 - It's a nice twist, I might consider it, though my current 'warp-mechanic' works well.
4 - Kinda like the magic mirror in ALTTP I presume?
5 - I'd rather keep bossfights a surprise (why not try instead of pretend?)
6 - Possibly, though I already have a talking sword for this purpose.
7 - Would this be a passive effect on the usual map system? I'm afraid I don't plan on using a quest-based approach...
8 - That was a neat mechanic, but it would require a game centered around this book concept. I like the limited approach, which forces some decisions, and I particularly enjoy the risk/reward of jumping into the book to defeat the demons and risk remaining trapped (it sounds worse than death).