Necropolis by Anthony Horowitz
This book seems a long time coming, but boy, was it worth the wait! It continues the tale of Matthew Freeman and the Guardians, a good versus evil saga that began 4 books ago.
The last of the Guardians is discovered in the shape of Scarlett, a year 11 girl, who is totally unaware that she has powers and that people are trying to kill her, until she goes through a door into another world and goes 'missing' for almost two days. Once both sides become aware of her and who she is, there's a race to get to her - but will Matt and crew beat the Old Ones? Why are they trying to lure the Guardians to Hong Kong and can they do anything to halt the horror and destruction that awaits them? Read on to find out, and prepared to be reading by torchlight as this is one book you will NOT want to put down!