How is Charlie an admirable hero in the book Charlie and the Chocolate Factory?

Charlie is admirable because he is an unlikely hero. He is
not selfish. He comes from nothing (poverty) in terms of financial wealth, but his
wealth is in the relationship that he has with his family and his willingness to give.
The other characters serve as a counterpoint to Charlie because of their obvious flaws.
Augustus Gloop is a glutton. An overweight child, he is always demanding more. He is
carried away when he falls into a river of chocolate because he was so quick to try to
drink from the chocolate river. Charlie has had to learn to get by on what he has and to
share with his family so that all will have enough to survive. Veruca Salt is spoiled.
She is the exact opposite of Charlie in many ways because she is always given what she
wants and has grown to expect that. She does not appreciate anything that she is given.
Charlie sees any gift, even the bar of chocolate and especially the golden ticket, as
much more valuable because he appreciates them. Violet is a gum-chewer who does not
follow directions. She is "punished" for that when she is turned into a blueberry! Mike
is addicted to television - something that was becoming popular in the late 1960's and
causing a growing concern that we still see today that children are becoming too
engrossed in the machines and not actively participating in
life.

Dahl created characters that are reflections of the
flaws that children learn that carry with them into adulthood. The character traits that
make Charlie admirable - selflessness, respectfulness, willingness to listen - are the
same traits that will make him a responsible adult. This is why Wonka chooses Charlie.
All of the other children are returned relatively unscathed (they are all in some way
altered by the experience physically), but Charlie, whose family needs the factory and
what it can bring to them the most, is the one who Wonka will bequeath his empire to.
The poor but honest hero becomes rich - but in many ways he was rich all along. He had
his grandfather's good guidance - a selfless man himself - to teach him the ways of the
world and that good things come to good
people.

Reference:

Dahl,
R. (1964) Charlie and the Chocolate Factory. New York: Knopf