A Fórmula de Deus (God's Formula), in English The Einstein Enigma, is the fourth novel written by the Portuguese journalist and writer José Rodrigues dos Santos, published in 2006 in Portugal.

The observer lurking in the shadows is CIA — fellow operatives are also close by, recording the conversation taking place inside the house between newly arrived Israeli Prime Minister David Ben-Gurion and his host, the word-renowned scientist Albert Einstein.

World-famous cryptanalyst Tomás Noronha is waiting on the front steps of the Egyptian Museum in Cairo when an attractive, dark-haired woman approaches and invites him to lunch in the Moslem quarter.

There, the cryptanalyst meets with two CIA operatives who warn him that the manuscript in question is in fact Einstein's recipe for an easily produced atomic bomb, commissioned many years ago by Israeli Prime Minister David Ben-Gurion.

Iran cannot be allowed to develop such a weapon: Tomás is assigned the mission of co-operating with the Iranians in order to ascertain the precise content of the manuscript and report back his findings.

Luís Rocha Assistant to Professor Augusto Siza, who collaborated with Einstein in the creation of Die Gottesformel and was kidnapped by the Iranians, helps Tomás in interpreting the results of the investigation into the manuscript.