Perusall (http://perusall.com) is an educational, research-based tool that creates a social media platform around uploaded materials or online materials. Students engage with the material, adding comments and questions that can be upvoted or commented on by other students in the class. Perusall can be used with published materials for a fee, but is completely free to use with open educational resources (OER). Perusall can automatically score students on their engagement with the material. This presentation demonstrates how Perusall has been used with an OER textbook in a introductory physics class.