Taleb is a pretty good writer, but I thought this was a very uneven book. As I read it I was constantly alternating between "Wow, that's a really great insight, a great way of presenting it" and "Gee, who doesn't realize that?", or even "That just seems flat-out wrong".
It's a book that should have been read by the quantitative analysts ("quants") working for the hedge funds and investment banks in early 2008; but it probably wouldn't have made much difference in the financial melt-down that followed. The problem with all their quantitative analysis was, as Taleb rightly points out, that it assumed that everything that could happen in the markets belonged to the domain of bell-curve events, and that hence probabilities could be computed for any possible market outcome. But "Black Swan" events (very rare, not even things we think about happening, and not linked to the factors that determine day to day market swings) do occur, they are of course unpredictable, and they can have massive effects. Some sorts of unpredictable events (such as unexpected conflict flareups, deaths of influential national leaders) are not Black Swan events because they are events we know about, and they are not really unexpected - only the timing is in doubt. Others, the real Black Swans, such as 9/11 and the derivatives bubble, have effects that play out over years.
But really, other than as a cautionary tale for those whose job it is to predict (unpredictable) things on a daily basis, these observations probably don't surprise most people who have thought much about the nature of reality and our grasp of the future. No one that I know owns a crystal ball. Without one even broad outlines of the future, that we believe are pretty certain, still have an element of risk/uncertainty; and perhaps a more significant element than we realize.
As the esteemed Donald (not Trump, the other one) pointed out, in one of his rare truly insightful comments, there are the unknowns that we know about, and the unknowns that we don't know about. It's the latter part of reality where the Black Swans live. (Of course, they also live in Australia, which is how the phrase got its meaning.)