Dark Victory: Red Vengeance

U.S Army Sergeant Randy Knox is sixteen, and already a seasoned veteran. He
is an alien killing prodigy who has
eradicated more of the invading Creepers
than anyone can keep track of. But Randy is also a high school student
struggling with geometry. And he is a young man whose heart is being pulled in
two directions by two very different
girls. One, Abby Monroe, a
straightforward warrior. The other, Serena Coulson, dangerous and
mysterious.
Randy, with the help of Serena's strange brother, alien
interpreter Buddy Coulson, has convinced a Creeper base to surrender. After a
decade of conflict, misery, and the death of millions of humans, it finally
seems that the war may come to an end. But then the surrender effort turns into
a bloody ambush. More disturbing, Buddy and Serena Coulson arrive, having
escaped torture and interrogation at the hands of a C.I.A. operative. It begins
to dawn on Randy that, as much as he doesn't want to believe it, the
powers-that-be may not want the war to be over.