Darwin revised his great book The Origin of Species through six editions between 1859 and 1872. This remarkable website by Ben Fry, On the Origin of Species: The Preservation of Favoured Traces, shows the evolution of every page of each of the fifteen chapters, color coded. The site loads slowly, showing you each successive revision as it ripples through the chapters.
If you were so inclined, you could read the whole book here -- scroll over the pages to see the revised words, again color-coded to the edition number -- but it would be difficult.
Fry is a master at data visualization. Take a look at his other work, including All Streets. Unfortunately, most of his work in genetics, and I'm just not versed enough to appreciate it.
(Found on TED, which found it on Nature's Great Beyond blog)
