I was by no means the originator of this idea of underdog or challenger brands. Many of the concepts we discuss, follow and build on have already been dutifully plowed over by marketing legends.
Here's a short list of books that are worth reading to delve deeper into the subject:
“Eating the Big Fishing” – Adam Morgan
“All Marketers are Liars” – Seth Godin
“Positioning” – Al Ries and Jack Trout
“The Brand Gap” – Marty Neumeier
“Johnny Can’t Brand” – Bill Schley and Carl Nichols Jr.