Roverandom by JRR Tolkien

Roverandom is an endearing adventure story — created by JRR Tolkien to comfort his young son who lost his toy dog on a seaside holiday. Out of that small heartbreak came a fun and exciting tale of a little puppy who gets mixed up in the affairs of wizards and ends up adventuring on the moon and down to the bottom of the sea. It's a sweet adventure everyone can love.