Steel Structure Supporting Pipe and Conduit

[Smart $]

The book says this, among other things. fault current is not "discharged" into the earth in typical low voltage system. why should I believe anything else in a book that starts out with something like this?

Because the book also covers grounding for lightning. If you think NEC only, your quoted statement will raise a flag. Under a broader scope of grounding, or should I say earthing, current from a lightning strike is considered fault current.