Yeah, it really gets to me that the people who are chanting "You must be true to THE ART, and only put in characters that are appropriate for the story THE ART wants you to tell" so often just coincidentally end up reading, recommending, and writing books that are overwhelmingly about straight white dudes. Apparently THE ART is a bigot?
So, books with protagonists/authors of diverse backgrounds:
Breadcrumbs, a bittersweet and brilliant MG retelling of a Hans Christian Andersen story, in which the protagonist is a PoC child adopted by white parents, in a midwest town where almost no one else looks like her.
Rivers of London (aka Midnight Riot), set in a London as diverse as it actually is, with a protagonist of mixed race.
Fox & Phoenix, a YA adventure fantasy novel of distinctly non-European derivation.
Liar, by Justine Larbelestier, has a mixed-race bisexual protagonist. (Also, there are maybe werewolves.)
From a different medium, Family Man is a webcomic (some of it also collected into graphic novels) with a Jewish-by-race, Christian-by-family not-quite-atheist protagonist in 1768 not-Germany. Also there are maybe werewolves. (Straight white man protagonist, yes, but there's a lot of complicated minority/Othering stuff going on with him and the eventual second protagonist, so I think it qualifies.)
The Amulet is a children's graphic novel series by Kazu Kibuishi that's strong, increasingly complex fantasy with great art.