While Joel has brought nothing new to the table in ways of farming (he merely fine tuned some ancient practices), what he has done is to re-introduce a word to the farmer's vocabulary: profitability.
His key to success has been
marketing. He can take his production and turn it into cash. As you read any of his works, pay special attention to what he is saying about creating/maintaining a market (for a product that grows itself). Anybody can raise chickens, but not everybody can
sell them for a comfortable profit. His books are certainly worth a read for anybody trying to generate some income from farming.