This is a Chrestomanci novel where Christopher Chant goes to a Series Seven world and meets and works with Conrad. Conrad has been suckered into trying to kill someone whose death will benefit his uncle, but things don't turn out quite like expected. Conrad and Christopher are both made Improvers at a large mansion -- one will be the Count's valet eventually -- and they find that someone at the mansion is "pulling the probabilities." They're changing tiny bits of the world magically in order to make money, but the changes happen more and more often and they're trying to find out what went wrong. Another very good book from Jones.
