The distinctive languages, art, and mythologies of the ancient Celts give archaeologists with an enduring quest in Northern Europe. The Celts rarely used their written language, passing along beliefs, knowledge, and wisdom through oral traditions. Artifact-rich burial grounds, like the megalithic tombs at Newgrange, Ireland, inscribed stones, and stone circles like Stonehenge, all yield clues to their mysterious ways.  (CLT05, $17.95)