Found in 2 comments on Hacker News
As Dale Carnegie said:

"Even in such technical lines as engineering, about 15% of one's [financial] success is due one's technical knowledge and about 85% is due to skill in human engineering, to personality and the ability to lead people."

In this sense a few books about mastering that 85%:

fuddle · 2013-12-05 · Original thread
I would recommend anyone interested in his life to read his autobiography, Long Walk to Freedom.

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