Which sentence states a fact?

 - Scott O'Dell's Island of the Blue Dolphins, which is about a girl named Karana, is a beautiful novel.
 - Island of the Blue Dolphins is based on the true story of a girl stranded on an island for eighteen years.
The second sentence states a fact.
Island of the Blue Dolphins is based on the true story of a girl stranded on an island for eighteen years.
It can be proved by reading the information on the book jacket.
The first sentence states an opinion.
Scott O'Dell's Island of the Blue Dolphins, which is about a girl named Karana, is a beautiful novel.
Beautiful shows what a person believes, thinks, or feels. Another person might have a different opinion about what makes a novel beautiful.