Darwin’s Origin of Species: A Biography by Janet Browne

A very accessible introduction to the life of Charles Darwin and his book that changed the world. This work is mainly a biography but also manages to provide historical context (and some future implications) for the idea of evolution by natural selection. Browne covers the influence of Lyell and Malthus on Darwin's thinking, the pressure from Wallace to publish, Darwin's sickly life, and his popularity in his day.

Tidbit:
As Darwin spent many hours examining barnacles his son mistakenly got the impression that that is what all fathers did. This is seen when he asked one of his friends, "Where does your father do his barnacles?"