Original: His book about games of chance, Liber de ludo aleae, written in the 1560s, but not published until 1663, contains the first systematic treatment of probability, as well as a section on effective cheating methods.
Simplified: A book of his, called Liber de ludo aleae (aproximately translates to as Book on the game of chances) contains the first systematic treatment of probability, as well as a section on how to cheat.