This is book 4 in Seven Wonders .

This book has been graded for interest at 8-12 years.

There are 320 pages in this book. This book was published 2016 by HarperCollins .

Peter Lerangis is the author of many books for young readers, including wtf , Smiler's Bones , the Watchers series, The Sword Thief , and the New York Times bestselling 39 Clues series. Peter lives with his wife and two sons in New York City. Visit him at PeterLerangis. com.