Hello!
Regarding the number of pages, it's not that there's a set maximum.
What happens is that I don't recommend making books that are too large or heavy, as the bigger they are, the more they could cause complications and delays when opening them in the game due to the amount of information they store.
I recommend that you divide the books into different volumes whenever possible to improve performance.
And based on your question, there isn't currently a built-in keyword search feature.
But once I update the plugin, I’ll consider it to see if I can incorporate it.
Best regards!