"On the Trail of the Golden Owl" by Max Valentin

In 1993, a mysterious puzzle began in France. A man named Max Valentin buried a golden owl, and launched a treasure hunt that has baffled treasure hunters for decades. 

All the clues needed to find the owl's location are hidden in the French book "Sur la trace de la chouette d'or" or in English  "On the trail of the Golden Owl."