The book by the same name demonstrates the divide between humans and chimps is quite wide, and not quite as close as the 98% DNA difference would claim. Now a statisical analysis, using 30 base stretches on DNA shows the true difference is much wider:-http://www.uncommondescent.com/intelligent-design/a-simple-statistical-test-for-the-alleged-99-genetic-identity-between-humans-and-chimps/#more-15043