The Crystal of Yggdrasil (Aki and the Spheres of Time, #1)
Achille Chiorri, known as Aki, believes he is a normal twelve year-old like everyone else; that is, until he discovers he has the power to travel to the distant worlds of the Parallel Crystals. With the help of a mighty artifact, the Sphere of Time, Aki goes on his first great journey and discovers that the gods and creatures he thought were only myths, are actually alive and all too real. Aki, together with an extraordinary girl and a special cat, is led by an elf of the Light as he travels through the realms of the Crystal of Yggdrasil, where he will encounter amazing creatures. To be able to return home, Aki must embark on a dangerous mission that leads to an exciting series of events full of twists and turns.