Research continues to demonstrate that motivated readers read more, yet too often students are not exposed to genres that might motivate them to continue reading. Further, students might not be encouraged to read outside their preferred reading genre. When students are unmotivated to read, they often do not read or do not finish the books they start. What would happen if students were encouraged to read from more genres and given the freedom to check out various genres of books from their school libraries? This study examines what happens to achievement and motivation when fourth-graders participate in a Genre Challenge that utilizes the Whooo's Reading app. Results indicate that comprehension scores in certain genres were impacted more than others, and while reading outside of the students' preferred genres did not significantly change, students did enjoy finishing books and were extrinsically motivated to finish the book so they could take the quiz on the app.