Loki

This is the first of three young adult novels from New York Times best-selling author Mackenzi Lee that explores the untapped potential and duality of heroism of popular characters in the Marvel Universe.
Before the days of going toe-to-toe with the Avengers, a younger Loki is desperate to prove himself heroic and capable, while it seems everyone around him suspects him of inevitable villainy and depravity ... except for Amora. Asgard's resident sorceress-in-training feels like a kindred spirit--someone who values magic and knowledge, who might even see the best in him.
But when Loki and Amora cause the destruction of one of Asgard's most prized possessions, Amora is banished to Earth, where her powers will slowly and excruciatingly fade to nothing. Without the only person who ever looked at his magic as a gift instead of a threat, Loki slips further into anguish and the shadow of his universally adored brother, Thor.
When Asgardian magic is detected in relation to a string of mysterious murders on Earth, Odin sends Loki to investigate. As he descends upon nineteenth-century London, Loki embarks on a journey that leads him to more than just a murder suspect, putting him on a path to discover the source of his power--and who he's meant to be.