When their grandmother Grace dies, orphans Amy and Dan accept a challenge to search for 39 clues that could make them the most powerful people in the world. But they aren’t the only ones looking. Other Cahills, more ruthless, wealthy, and powerful than them, have taken the challenge too and they are not willing to let a pair of poor kids beat them. In The Viper’s Nest, Amy and Dan follow a clue from Irina Spasky that leads them to Pretoria as they try to come to terms with the events in Australia.
Unlike the earlier books, this book felt informative but not particularly engaging. Not that it was a bad book, it just didn’t feel like we had as much character growth from the characters as we have in previous books. This is more about having Amy and Dan reacting to the events of the last book [if you haven't already read book six then this is a SPOILER: Irina Spasky died saving them in a fire--I don't know if I really believe she was gone, but it does seem likely] than about really delving into who they are. They come off as a little flatter and even perhaps slightly regressed, from the Dan and Amy we have come to know.
We do get a new surprise as Dan and Amy learn more about their ancestry and Amy remembers more about the night their parents died, but this is not really much in the way of character growth.
Ultimately, this book feels more like it bridges books six and eight than it does feel like a solid book on its own (sort of like the filler episodes on shows between episodes that are about the bigger mythology). It wasn’t bad, but it wasn’t great beyond the surprise at the end.