Angel City by Tony Johnston. Even though this is a picture book I'm pinning it in my middle grade section since it is emotionally intense--Joseph finds an abandoned baby in a dumpster and names him Juan. Joseph becomes Juan's Pop-pop and he raises him, teaching him about Joseph's African American culture and also Juan's Mexican culture. He tries to protect him from the violence of LA. The boy's best friend is shot and killed but they find love and comfort from each other.