Slow Decay, by Andy Lane
This is the second[*] of the three Torchwood tie-ins I bought, and I much prefer it to Dan Abnett's volume. Here, Tosh is intrigued by an alien artifact that has triggered a lethal brawl in a nightclub, while Rhys's work collegue Lucy has found a miraculous new diet, and appears to be showing an unhealthy interest in Gwen's boyfriend.
[* Although based on events related to incidental characters named in this book and the others, it should really be read last. I suspect the intended order is Second Life, Border Princes, Slow Decay. ]
[* Although based on events related to incidental characters named in this book and the others, it should really be read last. I suspect the intended order is Second Life, Border Princes, Slow Decay. ]