Clickers II: The Next Wave by J.F. Gonzalez and Brian Keene
The first wave was just the beginning . . . The United States is in ruins. It has just suffered one of the worst hurricanes in history, the people are demoralized, and the president is a religious fanatic. Then things get really bad - the Clickers return. Thousands of the monsters swarm across the entire nation and march inland, slaughtering anyone and anything they come across. But this time the Clickers aren't blindly rushing onto land - they are being led by an intelligence older than civilization itself. A force that wants to take dry land away from the mammals. Those left alive soon realize that they must do everything and anything they can to protect humanity - no matter the cost. This isn't war, this is extermination.