I don't really like the fact that you receive a book when entering a new world. I mean it's obvious that this is a modded item or something, and I think that you get it but it's not good for immersion → it's better when you're not like "ha yes this is an item from X mod".
So Idk if my explanation makes sense or whatever but it doesn't really matter in the end.

I got a suggestion to make this a little better : the main problem is that it only contains your mod's mobs, so it's a little strange, considering that this is a "bestiary". Shouldn't EVERY mob be in there??
You could simply fix that by adding vanilla mobs to the bestiary. It would make sense plus it would be quite fun to have a bit of lore/tips about vanilla mobs.

The only hic would be that mobs from other mods would not be in there.
If it turns out to be that much of a problem, maybe some mod integration could be done then?

(Oh and a config for not getting the bestiary at the start of a game would be cool too, we have JEI anyway..).

Your mod is really a blessing from the gods, thanks, really!!

not going to do this. we have enough language files to keep track of. besides im sure if you've figued out how to use mods/modpacks then you know what a pig or creeper is.