Charles F. Haanel is an important name to remember as he is perhaps the first to write on the law of attraction and how people can achieve anything they set their mind upon. Like Napoleon Hill, Haanel came from a humble background. At his death in 1946 Haanel was a very wealthy man and owned several companies. Haanel was of course not a conjure worker but his most famous work, The Master Key System (1914), would have been very attractive to hoodoo practitioners and conjure workers for it's use of the "master key" symbolism and it's text would most likely be viewed as a system of mental magic. As with Napoleon Hill, I highly recommend new conjure workers to read The Master Key System, and then follow this up with Napoloeon Hill's Think And Grow Rich.
If you would like to purchase the book then vist the link below.
The Master Key System by Charles F. Haanel
Indio/Wisdom Products also has a version of the book available as well. You can purchase it by clicking HERE.