[KMS] Event: Maple Secret Service

What is the point of the monster book anyway? Is there like an amazing reward for completing it, or is it like an in-game droplist or what?

The point is to provide a list backstory for every monster, provide an official drop list, a method to obtain *some* stats from in game, and just another thing to do. I doubt anyone knows if something happens when you complete it, because no one has and new monsters are being added all the time, so even if you did beat it in the next patch there'd probably be a dozen new monsters to collect, and 5 more cards for each of them...
You also get a 15% EXP boost off that particular monster once you have all 5 cards (though it only lasts for an hour.)

The point is that I'd get the horntail card from the anniversary (if it's availible...) And since it must be worth around 500k leaves, I'd be poor by the 5th D:


... Wait, am I even able to carry 500k etcs?...

you would need to be around level 150, even if it did let you buy Horntail cards, which I doubt.