In “Trenton: A Novel,” it is 1774 and the Revolution is brewing in the American colonies. This two-part saga begins with the discovery of a nearly lifeless body in the Delaware River, in Hopewell, N.J., by the son of a signer of the Declaration of Independence. The story of the Hart family, key players in the Revolution, is tied to the second part of the book, which takes place in modern-day Trenton and centers on the son of Cuban immigrants. Luis Alma is running for mayor and he discovers the key to Trenton’s future may lie in a secret from its past.