Hardback: 415 pages
Publisher: Folio Society, 2006
ISBN-10: None (but try 0674637526 for the Harvard University Press; Facsimile edition)
This is a reprint of Darwin's original first edition, from back in 1859. It's possibly the most important single book in history, and yet relatively few people have actually read it.
Darwin wrote a number of editions of this book, expanding (and arguably diluting) the arguments in it. What is illuminating when you read even this first one is just how much Darwin knew about Natural History, and just how long he had been thinking about the problems that the existing belief (in a set of individual creations, one for each species that had ever existed) raised. In the end, despite the fact that it was deeply radical by the views of the day, he just felt that those problems were rationally impossible to ignore. Everything he saw - the extreme age of the earth, the way that all mammals have the same arrangements of bones in their 'hands', whether whale flipper, bat wing, human hand or animal paw, the way the giraffe has the same number of bones in its neck as you or I, despite the obvious stupidity of doing it that way, the way that certain species of beetles have wing cases that cover wings, yet the wing cases are fused shut, the way that embryology points to the same development paths during much of pregnancy, etc. etc - all of these made a total mockery of the idea that a creator could have sat down and said "OK, today I do humans. And I'll give them toenails, because they'll look quite like apes, and apes have claws on their feet.".
So, having despaired of the pre-existing ideas, he looked at the evidence, and the evidence showed that animals and plants organise in varieties, and varieties organise in species, and species organise in genera, and so on up. And it was his realisation that this must be because they all descend from common ancestors (varieties recently, genera much further back). And then he shows how relative ability will cause some to survive better than others. And how that will cause a population to vary. And eventually, new species will arise.
The other thing that strikes the reader is that Darwin knew that people would be deeply sceptical, and would ask hard questions. There wasn't going to be some mass hypnotism and everyone was going to suddenly switch their opinions. He knew that his theory was an extreme one by the standards of the day, and extreme claims require extreme evidence. So he lined up every counter argument he could think of, and answered them all, in some cases admitting that the evidence was sparser than he'd have liked (most especially the fossil record, which is better today than then, but still incredibly patchy. Fossils just never happen. Well, they do, but your chance of being fossilised is vastly smaller than that of winning the lottery.). As a result, he put together a very strongly reasoned argument, that eventually persuaded every scientist in the field that he was right.
In the end, he answered, nearly a century and a half ago, every question that so-called 'Intelligent Design' is asking now. And more to the point, in rejecting the previous theories, he asked questions that today's ID people can't answer.
A scientific classic - and one that still answers the questions put to it.