On a shelf in a library in Texas sits a small green volume, originally published 150 years ago and now generally recognized as one of the most important scientific books ever written. Its future success was not at all apparent when this first-edition copy of On the Origin of Species was printed, however. As Charles Darwin finished the proofs of his new work, he drew up a short list of important colleagues who should receive advance copies. He then anxiously awaited the verdicts of the leading thinkers of his time.