"네가 읽어준 책은 무슨 책이었어요?"
Translation:What book was it that you read?
"What was that book you read" -sounds natural and should be accepted too.
Just reported it. Always report missing answers, they won't notice it here.
Why do you add 준 to 읽어? And not 읽은? At first I thought it was 읽어 주다 so what was the book you gave..?