It's funny isn't it. You go for years without reading a novel set in infinite dimensional Hilbert space, then along come two at once.
It's interesting to compare Brasyl, reviewed here earlier, with The Accord. In Brasyl, the many worlds of the Everett interpretation simply exist and the characters can access them, although it's not easy.
In Keith Brooke's novel, Noah Barakh is the architect of the Accord, the virtual reality to which people can be uploaded after their death on this earth. The Accord soon migrates to some kind of superpositional quantum state (physics a bit dubious here) where it turns out that there will be many Accord worlds in the usual manner. A kind of 'many virtual worlds' interpretation of QM then.
The Accord is actually a love story: brain and brawn competing for the feisty Priscilla. The brawn is elector Jack Burnham, a 'big man' who is used to getting what he wants and utterly ruthless in his methods. What he mostly wants is to possess his wife Priscilla and kill the man she has become attracted to, Professor Noah Barakh. This vendetta moves from real space-time to the Accord virtuality and then through many alternative virtual worlds.
Initially I thought the writing was a bit self-consciously clunky, but the pace soon gets up and the novel becomes a bit of a page turner. Brooke's characters are never less than real and what a scary bunch they are. He has a real feel for the dangerousness of powerful, implacable men. And this is a well-imagined description of what virtuality could really be like.
In the end this is geek action-oriented SF, in the way that, say, Richard Morgan's work is man-of-action action-oriented SF. In Myers-Briggs terms, NT vs. ST fiction.
Great novel, I'll have to look out for other stuff he's written (Genetopia).