Darwin wrote about ten books, though not all of them were about evolution or natural selection. Seven of them are listed here. Some of these books are still in print.
Journal of Researches into the Natural History and
Geology of the Countries Visited During the Voyage
Round the World of HMS Beagle . . . . . . . . . . . . . . . . . . . . . . . . . . . .1840
The Structure and Distribution of Coral Reefs . . . . . . . . . . . . . . . . . . 1842
Geological Observations on Volcanic Islands . . . . . . . . . . . . . . . . . . .1844
Geological Observations of South America . . . . . . . . . . . . . . . . . . . . 1846
On the Origin of Species By Means of Natural
Selection or the Preservation of Favoured Races
in the Struggle For Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1859
The Descent of Man and Selection in Relation to Sex . . . . . . . . . . . . 1871
The Expression of the Emotions in Man and Animals . . . . . . . . . . . . 1872