The Jefferson Key (Cotton Malone #7) by Steve Berry

Four United States presidents have been assassinated -- in 1865, 1881, 1901 and 1963 -- each murder seemingly unrelated. But what if those presidents were all killed for the same reason: a clause in the United States Constitution -- a clause that would shock the world?

In the most perilous exploit of his life, former Justice Department operative Cotton Malone must combat the Commonwealth, a treacherous, piratical society first assembled during the American Revolution. Along the way, he must break a secret cipher originally possessed by President Thomas Jefferson and unearth a centuries-old document which could make the Commonwealth unstoppable in its lust for power.

Genres: Thriller - Mystery - Historical Fiction - Adventure - Mystery Thriller - Suspense - Action - American Author