In Over Their Heads, 2

Nick and Eryn must figure out a way to save the world without sacrificing their newly discovered family in this follow-up to Under Their Skin, which Booklist called "crisp, intriguing, and thought-provoking" in a starred review.
In Under Their Skin, twins Nick and Eryn successfully met their new stepsiblings, Ava and Jackson. But in doing so, the twins found themselves on a mission to discover how to prevent humanity from facing certain doom.
Now, their two families are joined together to save not only themselves, but everyone—human and robotic. Can they figure out how before it's too late?

Margaret Peterson Haddix is the author of many critically and popularly acclaimed YA and middle grade novels, including the Children of Exile series, The Missing series, the Under Their Skin series, and the Shadow Children series. A graduate of Miami University (of Ohio), she worked for several years as a reporter for The Indianapolis News. She also taught at the Danville (Illinois) Area Community College. She lives with her family in Columbus, Ohio. Visit her at HaddixBooks.com.