You took me too literally (I reread my post and don't see how you took it that way, but it seems you did), but in reality they basically are the same book.
Yes, they're different authors at different times. The authors are just repackaging the same ideas.
The idea of taking positive thinking and affirmations and such to the extreme gets rehashed into a popular bestseller every few decades.
Think and Grow Rich, The Greatest Secret, and The Secret are all essentially the same book.
The original, TAGR, is probably the best incarnation, IMO, if you want to read one to see what the hype is about.