rationalskepticism.org

I have read it. It has some interesting anecdotes, but presents them in such a way as to make the importance of the salt trade seem much greater than it actually was. I think there's doubt about the historical accuracy of some of the "facts" in the book as well.

I did enjoy one of the recipes for using salt to preserve food - in the Confederacy (rebels in the US Civil War) they supposedly advised the best way to keep meat from spoiling in the summer - eat it early in the spring.