Of the lot of them, the one that matters most of all
"HE who wishes to decide whether man is the modified descendant of some pre-existing form, would probably first enquire. . ." and everything else written by Charles Darwin, now on-line, along with more than 170 ancillary texts.
I shall ever feel most thankful for the undeviating kindness with which I was treated, during our long voyage.
My Darwin Day resolution: Read these people more often.