Why was The Master Key system banned by the Church?

On Amazon it says that this book(which is also credited for helping Bill Gates and Napoleon Hill) was banned by The Church in the 1930s. Does anyone know why? Does that still stand? I can’t find anything else on the subject.

Its a ‘new age’ workbook/book.

That is probably why.

Not that I’m promoting this, but I was looking it up, and apparently, it was never banned by Catholic Church, according this website. thefreemasterkey.com/faq/

The only other place I could think to check was this banned book index, and nothing came up.
I did a search for the author, and nothing came back.

I have heard some judgements on this title having a New Age nuance, but that’s all I can say.

Anyone else have any experience with this title? I’m curious as well.

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