The Invaders (The Visitors Saga, #1), by Jay Ford, free
After an alien ship appeared in the United States, panic ensues. But almost as puzzling as its arrival, is when it suddenly leaves.
Taking almost the entire population with it.
Billions of people. Gone. That's the world seventeen year old Charlie Freeman lives in. The only person he knows of that's left is his cousin Alex.
Until the two of them find Sarah.
She tells them of survivors in Washington D.C., so they head down there from the ghost town of Boston. It was supposed to be an easy drive. But that all changed when the alien creatures that had been lurking in the shadows come to light.
Charlie is about to find out that he's not alone. He's the minority