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-all...

A new study that shows why we are so different. The 98% may be true if an uncritical lump of total human DNA and chimp DNA are studied, but looking at insertions and retro-transpositions we differ a great deal:

http://www.mobilednajournal.com/content/pdf/1759-8753-2-13.pdf