Exactly what the title would lead you to believe; a history of salt and civilization. Did you know that shoreline saltworks produce, not just table salt, but saltpeter, nitrates for meat-curing, and magnesium salts? There's a full-sized cathedral made out of salt in underground caverns below Salzburg. There are underground boating lakes, as well. Saltponds are red from brine shrimp, and flamingos are pink because they live on those shrimp. This book is full of great stuff like that.