A Ninth Doctor novel, set in the Powell Estate and featuring one set of aliens using computer games to recruit humans to fight their war against another set of aliens. The Sarah Jane Adventures did this too, with Warriors of Kudlak; I think this version of the story is better, with a lot of development of the Powell Estate, including a viewpoint teenager, and some nice Doctor / Rose moments. I've found Rayner's writing a bit hit and miss, but this was a good one.
Incidentally, I've noticed that on the whole the Ninth and Tenth Doctor novels with a contemporary setting are better than those with a historical or alien setting. I wonder if this says something about New Who? Or just that my sample size is small?