you know the bestiary in past ff games that allows you to look at the different enemies you encountered? I think it would be pretty neat if we had one in this game as well for the different enemies you killed.
Like how much health they have and what kinds of weakness they have to better defeat them but only if you find that out yourself then it becomes recorded in the book as well as how strong the different levels of the same enemy are. Like if you never seen the enemy then the page would be blank but when you kill the enemy you get its data but only some until you find other things about it like what items it might drop (useful for those crafting items) to its weaknesses and its strong affinity towards something.
There could be achievements for having a good number of monsters recorded as well and what the prizes of getting enough data I'm not sure at the moment but maybe a nice title maybe?
It might not be a carry around thing you take all over the place but maybe it could be placed in the inn room maybe on a table of some sort that you can look at any time you enter your room.
What do you all think of this idea? If you need me to explain more on this idea I could fix this topic up some and try making this as easy to understand as I can.