Wallace Wattles was the original Prosperity author, preceding Napoleon Hill by a couple of decades, and a founding philosopher of the New Thought movement.  Parts of his treatise almost sound like New Age "Quantum Quackery" (the blithering nonsense masquerading as science in "What The Bleep Do We Know?", though I admit the cognitive neuroscience segments were pretty good!) but having been written in 1910, Wattles' philosophy is rooted more in pre-twentieth century sciences—some of which are now obsolete (i.e., he seems to be familiar with the deprecated notion of an ether which permeates space) and some not—often embellished with a mystical pseudoscientific spin which is as charming as it is inspiring, albeit technically incorrect on many levels.

Nevertheless, the methods outlined in this book are EFFECTIVE if not entirely real on any so-called Metaphysical level, all grounded firmly in principles of Psychology—one of the "soft sciences"—but not "magical" as the author often makes them sound, especially in the first few chapters. Still, I suppose that's all part of the underlying psychological effect—the "Certain Way" works best, perhaps only, if you approach it with one foot planted firmly in the mythical realm.  Alas, if you think of it in purely psychological terms the magic sort of fades away. 

Ya gotta have faith, but it also takes action. Effort. Work. There ain't no such thing as a free lunch.

Noteworthy is that the book emphasizes the acquisition of wealth through CREATION of resources, as opposed to competition for them, eschewing the competitive business model which makes some persons rich at the expense of others.  Indeed, in a superabundant universe such as ours, there is no reason why everyone shouldn't prosper.  The problem isn't too many poor people, but not enough rich.