Halting State has an interesting and topical subject for a science fiction novel - an interactive web-game has been hacked by an unknown organisation who have stolen all of the virtual weapons and spells from their holding bank. Although the "bank robbery" is virtual, it nevertheless has serious repercussions for the product and the company who have developed it, since it is evidently going to affect sales of the game. It's a brilliant idea and the story flies along with plenty of incident and invention, Stross having a great deal of fun with gaming culture and those wrapped up in its worlds, while realising at the same time that it is a serious business.
The writing is quite dazzling, sparkling with sarcasm and humour (although bafflingly and for no good reason it is rather annoyingly all written in second-person - "you go here, and you do this" etc.), but it does become a bit heavy with tech-speak and eventually start playing out like a virtual game itself. It's clearly the intention of the writer to start blurring the lines between the real world and the virtual, but you'd probably have to be a gamer yourself to fully appreciate all the references and clever playing out of the situation.