It may be a children's book, but around the FBI, the bestselling Masquerade is serious business. The slim volume of baffling text and mysterious pictures by British writer and artist Kit Williams has sold nearly 1 million copies around the world. One reason for the book's appeal: somewhere in the British Isles, Williams buried a hare-shaped amulet made with seven ounces of gold. And the clues for finding the cache are contained in the book's words and illustrations.

The book's American publisher, Schocken Books, received last month an official purchase order for a copy of Masquerade from the FBI.

"I think those G-men are trying to crack the case, don't you?" asked Irene Williams of Schocken.

Not so, says the FBI.

"It's been purchased by our laboratory that contains the section on cryptanalysis," says FBI spokesman Ed Gooderham. "They'll use it for training purposes, to keep abreast of cryptographic styles published around the world."

Indeed, according to Newsweek magazine, Masquerade aficionados make use of "everything from astrology to trigonometry to fathom its mystical text and complex art."

Will the G-men go for the gold?

"I doubt it," says the FBI's Gooderham.