The book you might be referring to is "The True Believer" by Eric Hoffer. Published in 1951. It's about 175 pages. If you've ever wondered why political correctness, BLM and anti-racism resemble a religion (non-theistic) it is definitely worth a read.

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I would have liked to remove the part about political correctness, BLM and anti-racism as it does nothing to contribute to the discussion and the question can be answered without a reference to any of those things. I will not, because to do so feels misleading.