To me a heroine in a novel has to have achieved something, whatever it may be. She has to be a strong character who puts others before herself. Also she must have an understanding of what's right and wrong in life and be determined to reach her aim and never give up. She doesn't have to be the cleverest and prettiest of the group but she does have to be capable and brave, someone you can depend on. After reading "Is," I feel she has many of these qualities.
I would say that Is was the main heroine in the novel, but you could also say that many of the other characters had some of the qualities I mentioned above. It first tells you in the title of the book that Is is probably the main character, who is focused on the most, and you can usually say that she will be a heroine somewhere throughout the novel.
As in most books that have a name of a character in the book as the title, such as "Jane Eyre" and "Oliver Twist," this is true.
The novel is focused on Is who sets out on a journey to the so called "Playland," to find her cousin Arun Twite and the king's son Davie Stuart who have both gone missing along with many other children. Is travels north to Playland, which turns out to be an underground kingdom called Holdernesse run by "Gold Kingy," otherwise known as Roy Twite, Is's wicked uncle, where all the children work as slaves in the worst conditions imaginable. Is manages to escape from being made to work in the mines and goes to live with Aunt Ishie, her grandmother and Grandfather Twite, her great-grandfather. Is has many attempts at trying to help...