Jennifer Michael Hecht noted in her review of the book that Ingersoll was most noted for his quips, which have survived down the years. Apparently, it was this wry sense of humor that endeared him to so many followers during his time. He also had his fair share of detractors, past and present. I noticed that David Barton took a swipe at Ingersoll in his book on Jefferson.
Jacoby tries to figure out what it was that made "Fighting Bob" an American original, and also why his voice of reason hasn't fared as well as others over time. Mark Twain is a household name. Robert Ingersoll is the kind of guy who pops up in trivia games.
It seems you had to hear him speak to feel the full weight of his arguments, and sadly no voice recordings have survived. We can only imagine what his printed speeches might have been like from anecdotes like the one Hecht provides of Eugene Debs buying a train ticket from Terre Haute to Cincinnati just so he could stay with Ingersoll a little while longer after having heard one of his famous speeches.