Google Docs recently added some new templates in their template gallery. The Book Report Template created by Reading Rainbow is just one that is worth taking a closer look at. It provides a basic book report structure including prompts to get students thinking about setting, characters, and the plot. The template includes prompts for students to include images that relate to the book and their descriptions. Your students could use the template "as-is" or you could use the template as a starting point to create your own book report template that meets the needs of your students and class.
If you haven't visited the template gallery before, it is easily accessible via the landing page for docs. You can reach the landing page through the apps launcher and clicking on the docs icon.