Real Planet Nine — Paul Park

A drive across the desert leads Durant and his younger brother and sister to their Aunt Rachel's house for the first time. Expecting a dull, hot summer in the New Mexico desert and faraway from their California home, they've heard rumors that their aunt has been up to something strange in the mountains behind her backyard. Soon, the children learn that Aunt Rachel is on the verge of discovering a secret older than human history. What they don't know is that they are about to embark on a journey that will take them to places beyond their wildest imagination. Going along for the ride has taken on a whole new meaning.