1. Darwin, C. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (John Murray, 1859). This book is essential reading for those who wish not only to understand evolution in general but also to see the wealth of Darwin's original ideas that have yet to be tested.
2. Wallace, A. R. On the tendency of varieties to depart indefinitely from the original type. J. Proc. Linn. Soc. (Zool.) 3, 53–62 (1858).
3. Rudwick, M. J. S. Bursting the Limits of Time (Univ. Chicago Press, 2005). This book provides the best explanation for how it became evident that fossils represent the history of life and how the geological timescale was developed.
4. Mayr, E. Reasons for the failure of theories. Phil. Sci. 61, 529–533 (1994).
5. Mayr, E. Systematics and the Origin of Species (Columbia Univ. Press, 1942).