Questions about the Monster Book in other versions.

The Monster Book can't be completed right now.
If you're high-level enough to be collecting, say, skelly cards, then perforce you can't meet King Slime, Alishar, or Papa Pixie to collect their cards.

We need an event that allows "buying" cards of those level-limited pq bosses, to make it even theortically possible to have a complete book.

Yeah, I hope they have an exchange, during 4th anniversary, to trade Maple Leaves for those unobtainable monster cards.
I, for one, will be completing the entire book one day... regardless of how long it takes.