Which sentence states a fact?
Jeff Kinney worked on Diary of a Wimpy Kid for six years before publishing it online. Cartoonist Jeff Kinney's book Diary of a Wimpy Kid deserves all of the praise it has received.
A fact is something that can be proved by research or observation.
Napoleon Bonaparte was shorter than King Louis XVI.
The statement above is a fact. The statement can be proved by researching the height of each man and comparing them.
An opinion is something that a person believes, thinks, or feels. An opinion cannot be proved.
Napoleon Bonaparte was a better leader than King Louis XVI.
The statement above is an opinion. People can have different ideas about what makes someone a "better" leader, so the statement cannot be proved.
The first sentence states a fact.
Jeff Kinney worked on Diary of a Wimpy Kid for six years before publishing it online.
It can be proved by reading a biography of Jeff Kinney.
The second sentence states an opinion.
Cartoonist Jeff Kinney's book Diary of a Wimpy Kid deserves all of the praise it has received.
Deserves shows what a person believes, thinks, or feels. Another person might have a different opinion about how much praise Diary of a Wimpy Kid deserves.