I've just finished reading Janet Browne's book Charles Darwin's Origin of Species: a biography. Apart from a couple of howlers with dates, it is a thoroughly good read. One passage I particularly enjoyed:
Darwin called this shorter book [On the Origin of Species] 'one long argument'. And what an argument it was. Few scientific texts have been so closely woven, so packed with factual information and studded with richly inventive metaphor. Darwin's literary technique has long been noted for its resemblance to Great Expectations or Middlemarch in the complexity of its interlacing themes and his ability to handle so many continuous threads at the same time. Hardly daring to hope that he might initiate a transformation in scientific thought, he nevertheless rose magnificently to the occasion. His voice was in turn dazzling, persuasive, friendly, humble and dark. His imagination soared beyond the confines of his house and garden, beyond his debilitating illnesses and the fragile health of his children. At his most determined, he questioned everything his contemporaries believed about living nature, calling forth a picture of origins completely shorn of the Garden of Eden and dispensing with the image of a heavenly clockmaker patiently constructing living beings to occupy the earth below. He abandoned what John Herschel devoutly called the 'mystery of mysteries' and replaced Paley's vision of perfect adaptation with imperfection and chance. Animals and plants should not be regarded as the product of a special design or special creation. 'I am fully convinced that species are not immutable,' he stated in the opening pages.
I think that summarises Darwin's masterpiece rather well.
The next time some idiot tries to tell you that On the Origin of Species is not very well written, why not refer them to the above passage?