i hate it when people ask about drop rates. me telling you it's about 0.1% per mob doesn't mean it'll take you a thousand mobs to get one... it's rolled for every single time you kill one, therefore the chance you'll get one is always 0.1% assuming that's what its drop rate is.
just kill stuff and get monster cards; if you're really interested in maxing out the book, you'll persevere.
It depends a lot on the monster's level. I think on average the drop rate is around 1/800, while lower level monsters are probably as high as 1/200, and higher levels are probably as low as around 1/1500. Area bosses on the other hand I think have a drop rate of around 1/400. That's my guess.
The reason why it's often not good to start talking about droprates (though they are known) is because situations like this:
We now tell you what the droprate is. Week later, you come "OMG TEH DROPRATE WAS 0.1% BUT I KILLED OVER 3000 MONSTERS WITHOUT CARDDROP THAT DROPRATE IS BROKEN" because you didn't understand how it works.
Your Existance is a plothole - Kaiolini You aren't on YouTube so this makes your topic not real so hurhurhur. -Drekerr