For years I have had the highest respect for N. N. Taleb.  He was the guy who wrote the book (The Black Swan), as well as some others on finance and how so many "experts" are complete phonies.

Fooled by Randomness (I would start with this one if interested in his ideas) and Antifragile are also extremely good reads of his.

A "Black Swan" is an unexpected, low probability event (usually negative) that has a large impact.  Think 9/11...  Unexpected.  "Low Probability" (impossible to predict).  HUGE impact.