Found: it's driving me crazy that I can't remember the name of this nonfiction fantasy/science fiction book

I need help finding a fiction fantasy book. I don't remember the title and my details are limited. I remember it was a fantasy adventure book. There was a monster that was going to school and she was kind of an outcast. I think there was a human in it as well. They went on an adventure together. I think the cover was blue and there was a picture of them driving in either a Cadillac or a VW bus on the road to their adventure. I know that's not much to go on but I'm hoping someone can help me.

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When was it likely to have been published/ when did you read it?
What age group was it aimed at?
Where was it set/ likely to have been published ie US/ UK/ etc?

Was it Helen and Troy's Epic Road Quest by A. Lee Martinez? It's fiction, but I think that's what you meant. Helen is a minotaur. The cover is bluish, and they're driving a convertible.

I read it between 2013 and 2014. It was a young adult book. It was published in the US.

Found it: Holy crap that's the book. Thank you. I never thought I would remember this book.

Touchstone: Helen and Troy's Epic Road Quest by A. Lee Martinez