vocabulary - What is "opening her Caesar" referring to here?

"But, oh, Marilla, I really felt that I had tasted the bitterness of
death, as Mr. Allan said in his sermon last Sunday, when I saw Diana
go out alone," she said mournfully that night. "I thought how splendid

it would have been if Diana had only been going to study for the
Entrance, too. But we can't have things perfect in this imperfect
world, as Mrs. Lynde says. Mrs. Lynde isn't exactly a comforting
person sometimes, but there's no doubt she says a great many very true
things. And I think the Queen's class is going to be extremely
interesting. Jane and Ruby are just going to study to be teachers.
That is the height of their ambition. Ruby says she will only teach
for two years after she gets through, and then she intends to be
married. Jane says she will devote her whole life to teaching, and
never, never marry, because you are paid a salary for teaching, but a

husband won't pay you anything, and growls if you ask for a share in
the egg and butter money. I expect Jane speaks from mournful
experience, for Mrs. Lynde says that her father is a perfect old
crank, and meaner than second skimmings. Josie Pye says she is just
going to college for education's sake, because she won't have to earn
her own living; she says of course it is different with orphans who
are living on charity—THEY have to hustle. Moody Spurgeon is going to
be a minister. Mrs. Lynde says he couldn't be anything else with a
name like that to live up to. I hope it isn't wicked of me, Marilla,
but really the thought of Moody Spurgeon being a minister makes me

laugh. He's such a funny-looking boy with that big fat face, and his
little blue eyes, and his ears sticking out like flaps. But perhaps he
will be more intellectual looking when he grows up. Charlie Sloane
says he's going to go into politics and be a member of Parliament, but
Mrs. Lynde says he'll never succeed at that, because the Sloanes are
all honest people, and it's only rascals that get on in politics
nowadays."

"What is Gilbert Blythe going to be?" queried Marilla, seeing that
Anne was opening her Caesar.

"I don't happen to know what Gilbert Blythe's ambition in life is—if
he has any," said Anne scornfully.

–– L. M. Montgomery, Anne of Green Gables

Answer

I assume it means that she was opening her copy of ‘De Bello Gallico’, Julius Caesar's comentary on his campaign in Gaul.