A book called Dreadnought by April Daniels.
It's about a teen trans girl who is transformed into how she thinks she should be when a superhero (Dreadnought) falls from the sky, transfers his power onto her and then dies. So she has to deal with living in a body that fits her, her psycho dad, her best friend who now wants to date her and other superheroes who think she's too young to take over Dreadnought's powers.