Jefferson Key by Steve Berry

Four presidents of the United States have been assassinated—in 1865, 1881, 1901, and 1963—each murder seemingly unrelated. But what if those presidents were all killed for the shocking same reason: a clause contained in the United States Constitution? This is the question faced by former Justice Department operative Cotton Malone. When President Danny Daniels is nearly killed in the heart of Manhattan, Malone risks his life to foil the murder—only to find himself at odds with the Commonwealth, a secret society of pirates first assembled during the American Revolution. Racing across the nation and taking to the high seas, Malone and Cassiopeia Vitt must break a secret cipher originally possessed by Thomas Jefferson, unravel a mystery concocted by Andrew Jackson, and unearth a document forged by the Founding Fathers themselves—one powerful enough to make the Commonwealth unstoppable.

My Take:  I love a good conspiracy theory and this book held my interest.  If you are a history buff and mystery enthusiast, you should enjoy it.  This is a new author for me but I would like to read more from him.  It's a book a can recommend.