How does Artemis’ character develop during the course of the book?

Despite the fact that Artemis does not feel sympathy for those who are not in his immediate circle, he experiences some character growth over the course of the novel. As he spends more time with Holly, he begins to feel bad for how he is treating her. Despite this, however, he keeps her as a hostage until the very end. He does eventually give her her half of the ransom when she is released, but only when she grants him a wish.