The Fifth Stone is a story of friendship, evolution and personal growth that relates very directly to the interests of readers between the ages of 10 and 12 years old. Readers will find in its pages some of the elements that make a YA novel particularly attractive: • a mystery that involves the reader who accompanies the protagonists in their discoveries throughout the book. • The portrayal of personal conflicts and difficult situations which the characters must solve or overcome in order to progress and grow in maturity. • The appearance of those first adolescent feelings, so powerful and passionate, which overflow and get mixed up in the story. • Enigmas in the plot itself related to numerical, spatial and geometric concepts suitable for this age.