I also think David handles the relationships brilliantly here. Forget love triangles, we get a virtual love octagon as Archie is a teenage boy with a hyperactive libido and a short attention span which sees him bounce around from girl to girl, with Ty and Archie's friend Oscar on the outskirts with their own attempts at romance. As ever with David, the sexual tension - as well as providing a nice contrast between Archie's ever-changing attraction to various girls and Ty and Claire's much deeper feelings for each other - adds to the drama rather than distracting from the main storyline.
Strong recommendation which cements David as one of the very best thiller thriller writers out there for either adults or teens.
For another incredibly tense thriller, don't miss [[The Long Weekend by Savita Kalhan]].