If you blend science fiction, mystery, espionage, archaeology, science, math and adventure, you have a book fascinating for ages 8 through adult. So many historical facts, innovations and locations are mentioned making this an excellent read a chapter and then do an Internet search on the person, place or things mentioned to enrich your knowledge. Do you know about Peru's Gate of Amaru Muru? This adult reader didn't as it was discovered in 1996 which I learned about from extra research with young male readers who enjoyed the Internet searching of what they didn't know about. Having visited several of the European locales mentioned, descriptions are perfect. If a youngster reads this on his or her own, because it is filled with so much factual information, one may come to think some of the science fiction elements are real too- but then, who wouldn't want the ability to turn invisible? Math and science is so beautifully blended into the plot the young reader can learn so much and enjoy a good adventure story at the same time. The novel ends with the plot lending itself to a sequel of the task given to twins Declan and Dayla as a quote in the book says, " Humanity depends on your secrecy."(79) I happily received a copy for review from Goodread First Reads.