I especially became interested in reading this again when I began to think about the notion of “preservation of favoured races in the struggle for life”.
On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life (Harvard Paperbacks), Charles Darwin, Ernst Mayr. $15.66
https://www.amazon.com/Origin-Species-Harvard-Paperbacks-ebook-dp-B00IUF9L0W/dp/B00IUF9L0W/ref=mt_kindle?_encoding=UTF8&me=&qid=1545847758
This, the most interesting and helpful edition of Charles Darwin’s major work, is now available in an inexpensive paperback edition. It is written with clarity, forcefulness, and conciseness not found in any subsequent revision. For modern reading and for reference, it is the standard edition.