Are there novels that focus on a protagonist who is a monster, but explores their nature beyond just being evil?

Yes, the concept of a protagonist who is a monster, but whose story delves into their nature beyond simple villainy, is definitely explored in some novels. "Realm of Monsters" is a prime example of this. The description highlights Stryg, a "determined goblin outcast," and emphasizes that the novel explores "monstrosity beyond appearances." This directly addresses your interest in understanding a monstrous character from a different perspective.

This kind of narrative often challenges the reader's preconceived notions about what it means to be a monster. Instead of portraying them as inherently evil or purely destructive, such stories delve into their motivations, their struggles for survival, their capacity for loyalty, or even their desire for acceptance. The "School Life" category for this novel suggests that Stryg's journey might involve learning, growing, and interacting with others within a structured environment, further allowing for the exploration of his character beyond his monstrous identity. It's a compelling way to examine themes of prejudice, identity, and the gray areas of morality.