The man had a sense of humour and did not, apparently, take himself as deadly serious as some of his modern proselytes do.
By which I do not want to imply any basic anti-Darwinism on my part, but a certain allergy to dogmatic hair splitting, noticed when reading some current discussions of Mr.Darwin's legacy.
The best parts of the book, for me, are those where he light-handedly defines his relation to predecessors, influencers, peers and successors, like e.g. his grandfather Erasmus Darwin (and his version of evolution), or Thomas Malthus (on populations and selection pressure), like Alfred Wallace, who co-fathered the theory of evolution by natural selection (and whose Malay Archipelago is my favorite travel book of all times), or like Herbert Spencer (the man about 'social Darwinism'), with whom CD disagrees completely.
I also like CD's thoughts on religion. One moment he defines himself as a definite atheist (regarding a personal interfering god), which surprised me, I did not think he was so clear about that. But then, next page, he backtracks and calls himself a theist in some other way of looking at things (the preceding intelligence). Then somehow he concludes that he is an agnostic. Sound attitude.
He does not really spend awfully much time and effort on this memoir, and that determines the easygoing character of this highly readable book. A must for all who are interested in 'the meaning of life'.
This edition by N.Barlow adds back some texts which had been purged by the family for this or that reason. That is a good thing. Unfortunately she also adds the whole dreary controversy called the Darwin-Butler disagreement, which is wholly superfluous.