The Science of Success by Wallace D. Wattles is three books in one. It includes, The Science of Getting Rich, The Science of Being Well and The Science of Being Great.
The Science of Getting Rich is the book Rhonda Byrne says gave her the inspiration for ‘The Secret’.
The three books are based around New Thought Principles that Wattles was a proponent of. I felt it was an interesting read that has sparked an interest for learning more about who came up with these ideas before Wattles and his peers. It is thought the earliest proponent of New Thought was Phineas Parkhurst Quimby (1802 – 1866).
Ralph Waldo Emerson and Henry David Thoreau are commonly quoted in all the books. However, Wattles always goes back to the Bible for quotes to back up his theories. So maybe the first ever Self Help or New Thought book was the Bible. In the books he tends to repeat himself to explain a principle and ingrain it in you. Not the easiest read but I recommend it if you are interested in The Secret and want to learn more about what you can do and be.