It could be 'Harry Potter'. In the series, there are many magical and unexpected things, and a toy - like object coming to life, like a spider jumping out, would fit right in with the magical world J.K. Rowling created.
He might be trying to escape from someone or something. He probably thought jumping was his best option at that moment. However, he could face serious consequences, not only from the fall but also from the theft he committed.
Maybe MJ. She could be in the area and use her quick thinking. She might find a large awning or something to break his fall, or she could call for help from nearby superheroes like Daredevil who could swing in and save Peter.
Since he's a comic book thief, he could be a comic book fanatic who couldn't resist stealing them. As for his appearance when jumping out of the second story, he might be in a hurry, with his clothes in disarray and a panicked look on his face.
I'm not sure what you want to ask about the novel. Can you provide more specific questions or information? I will try my best to provide you with useful answers.
Armin could be the storyteller. Sometimes characters take on this role to provide a unique viewpoint or to drive the narrative in a particular direction. But we need to know more about the story to confirm it for sure.