Come to think of it, it's a tricky problem to write a whole book debunking something as utterly ridiculous as the "law of attraction." My first thought is to leave it to the experts at CSICOP, but I doubt many Christian booksellers stock titles by professional atheists.
Human brains are very good at detecting patterns, and at creating patterns where there are none. Telling people, "Whatever pattern you think may be caused by a law of attraction doesn't really exist," probably won't work in a culture where lotteries are multi-billion dollar industries.
Better, I'd say, to give them the pattern of the Gospel, compared to which any other pattern that might fit a human life is as straw to gold.