It is truly just an edited and rather advanced rendition of James Allen's "As a Man Thinketh". In that particular book, every single thing is penned in a poetical or even biblical manner. Consequently, it poses no easy feat for an average reader to fathom that book.
Therefore, James Allen's brother, Marc Allen, took it upon himself to edit this book. He did so by using normal English, which makes it more accessible. Additionally, he incorporated several examples to facilitate easier understanding. And indeed, this is a very good thing.
If you happen to be an average reader, I would highly recommend this edited version rather than directly delving into "As a Man Thinketh". However, if you possess the ability to understand that original book, then by all means, go ahead with it. The choice ultimately lies in your own reading capabilities and preferences.