Giannine's character, Janine de St. Jehan, is the illegitimate child of the recently deceased King Cynric, who pronounced her heir to the throne, passing over three legitimate sons.

Janine finds herself on a sheep farm, where she meets her foster mother and Sir Deming, who delivers the news of her ascendancy to the throne.

Back on the farm she finally rushes at Sir Deming in frustration and tries to bite his ring off his finger, but he takes out a knife and stabs her.

At the castle, barbarian invaders led by King Grimbold kidnap Janine, hoping to ransom back a crown they claim Cynric stole from them.

She learns that Cynric gave the stolen crown (which grants the wearer a temporary Midas Touch) to a dragon that terrorized the land many years earlier.

The next day, a meeting with magicians is interrupted by an attack by Grimbold's people, who send a message that they won't stop until Janine is dead.

Unlike the previous times, she listens to the evidence with an open mind, makes Kenric feel like he's taking part in the decision, and sentences the boy to a month of hard labor rather than killing him or freeing him.

The book takes place in Rochester, New York sometime in the twenty-first century future, but the game is set in medieval Europe.

In her book Constructing Adolescence in Fantastic Realism, Alison Waller discusses Heir Apparent along with several other young-adult novels about virtual reality.

She writes that the fact that these novels take place almost entirely within the virtual world suggests "that problems of real life can best be solved within this expressly adolescent space, or that VR environments are inherently more exciting or interesting for teenage readers.... Vande Velde maintains an ironic connection between the fantasy world and a peripheral real world and this minimises the dramatic tension of events within the virtual reality game: we are always aware that Janine's heroic actions and decision-making find reference points in Giannine's real (and in a way rather ordinary) adolescent concerns.... 'Heir Apparent' acts as a space in between the real social relations Giannine faces at home and the virtual adventure she has to tackle as Janine.