The Fifth Wave by Rick Yancey

No one is safe after the fourth wave of attacks by the Others, even though the children who have been taken into custody are repeatedly told, "You are perfectly safe." In this fast-paced, intense sci-fi thriller, teenager Cassie Sullivan is on a mission to find her little brother Sammy. Her last image of Sammy is of him waving happily from the back window of a schoolbus, which was taking him to safety. Or so she thought.
This is an action-packed survival story that will keep readers up late into the night. It has strong, interesting female and male main characters that will appeal to readers. I recommend this book to readers who like action, adventure, survival stories, and a little bit of science fiction. This book would be a great start into the sci-fi genre since it seems very realistic--especially for those who believe that we are not the only intelligent life in this galaxy.