From the introduction:
What if the monsters in the Forgotten Realms masked their appearances as humans and non-humans? What if after several centuries, these monsters managed to create a civilization, the Vendrian. A population of highly intelligent monsters that can look like a tavern keeper, or a peasant?
Elandria is a campaign setting book that seeks to challenge players perception of good and evil, by stripping monsters of what makes them easily identifiable. Now you don't have the luxury of knowing if the gnome you are talking to is actually a gnome, or a Goblin. Or if the half-ogre you found is dangerous, or just lost in a world that doesn't comprehend him.