The sixth book of nine in the series, brings back Mallory and Sophie from The Devil in Green. This book in some ways is much darker, somewhat more human, showing the disparate aims of society, pockets of resistance and government agencies trying to gain order and control.
Magic and technology work side by side, as the world continues to spiral towards eternal winter and eradication of all life.
There are more mysteries and myths to untangle with time running out as the opposition becomes stronger.
This book also brings back Laura, Ruth and Shavi of the original five but Ryan and Jack seem to have become myths themselves.
There is a lot of action but it is well paced and for the Trilogy of Trilogies fan it will not disappoint but leaves you eager to start the next set Kingdom of the Serpent.