The Enchanted Castle is a captivating and intricate story, featuring a gripping plot, engaging characters, and Nesbit's expert mix of magic and realism. The narrative is both dynamic and inventive, with episodes that range from humorous to frightening, and from adventurous to mystical. The four young main characters are well-developed and entirely believable, each possessing strengths and flaws that make them intriguing. The plot's transition from pretend magic to genuine magic is subtle and convincing.

Nesbit's inclusion of various ideas in her story adds further interest. Her combination of realism and enchantment provides both social history and domestic magic. She vividly portrays Edwardian family life with rich detail. While Nesbit never overtly preaches, she subtly conveys a moral perspective that emphasizes individual honor and integrity. Despite the many opportunities granted by the ring of invisibility, the characters never misuse their magical powers to harm or deceive others. Her central, overarching theme is that magic exists in everyday life for those who are perceptive and imaginative enough to notice it.