Falling skies - Paul Tobin

In the heart of Boston, following the devastating events of an alien invasion, history professor Tom Mason and his sons Hal, Matt, and Ben are just trying to survive. After an extreme firefight with the aliens, Ben gets kidnapped. Determined to get his son back, Tom joins forces with the 2nd Mass, a militia group that is taking the fight against the aliens. But with the group's munitions supplies running low, Tom must locate an old friend to equip him and his team in order to ensure the survival of the human race!