I had a similar project to do last year, the only difference being that my city's Board of Education chose the book. It was, "The Boy in the Striped Pajamas" by John Boyne. It was a quick read, but is an extremely good novel. There is also a movie about it if you'd rather read that instead.
We had to upload our writing for online evaluation by the teacher, and I'm not planning on taking mine down (mostly because I don't know how to delete the site lol), so you can check it out.
Also, feel free to email me if you have any questions or need additional help - firstname.lastname@example.org (<- don't judge me! :P)
Hope I did some good!