"The Da Vinci code"

This book describes the attempts of Robert Langdon, Professor of Religious Symbology at Harvard University, to solve the murder of renowned curator Jacques Saunière of the Louvre Museum in Paris.
A baffling cipher is found near his body. Saunière's granddaughter and
Langdon attempt to sort out the bizarre riddles and are stunned to
discover a trail of clues hidden in the works of Leonardo Da Vinci.

The unraveling of the mystery requires solutions to a series of simple brain-teasers, including anagrams and number puzzles. The ultimate solution is found to be intimately connected with the possible location of the Holy Grail and to a mysterious society called the Priory of Sion, as well as to the Knights Templar. The story also involves the Roman Catholic organization Opus Dei.