Should I write the midterm tmrw or write a final worth 100%?

Ok so I have an easy Prejudice psychology course, I have a midterm tmrw and I just bought the book today!!!! This never happened to me before!! I read 2 chapters out of 5! Im screwed! I can just not go to my midterm tmrw but the final exam is gonna be worth 100% of my grade! I don't know what to do! Please help!