Unlike many of those who discuss the subject today, Stephen Jay Gould had a very positive and non-defensive approach to discussing evolution. "Ever Since Darwin: Reflections in Natural History" is Gould's first book and is a collection of essays which Gould wrote between 1974 and 1977 for "Natural History Magazine". These are organized into 8 sections which cover everything from the basics of Darwin's theory through applications of that theory to the evolution of humans, through the history of life on Earth and the view and role of science in society. All in all there are 33 essays included on a diversity of sub-topics involving the theory of evolution, though certainly some points are repeated as one would expect when dealing with individual essays on a related subject.
Stephen Jay Gould's writing is easy to read, and these essays are targeted to people interested in science, but you don't have to be a scientist to understand them by any means. Gould also makes the reading more entertaining by including interesting bits of trivia, such as covering who was the naturalist aboard the Beagle, correcting many bits of misinformation regarding Darwin and his theory, and discussing why Darwin waited so long before publishing. Unlike many more recent books (this book was originally published in 1977), Gould avoids getting drawn into the name calling which goes on between creationists and Darwinists.
Gould's enthusiasm for the subject comes through in his writing, and his passing in 2002 from cancer was a great loss to science, as well as to the public discussion of science to which he offered a thoughtful and insightful voice. That is not to say that Gould was never the focus of controversy, as he forced evolutionary biologists to rethink some of their ideas due to his ability to view things from a different angle. Some have claimed that his theories, such as punctuated equilibrium which he developed with Niles Eldredge, were never more than what was already contained in the theory of evolution, but I still see the echoes of his approach in many recent articles about evolution.
I have heard some people claim that Gould later decided that "Ever Since Darwin" was his worst book, though I have never been able to verify this claim. It wouldn't surprise me if that were true, as many authors cringe when looking back on their earliest works. That being said, I think the essays in this book still offer a wonderful place for those who are interested in the subject to get a good understanding of the subject and the theory. Of course, given that it was published in 1977 there is so much more that has been discovered that this should not be the only resource that one uses, especially if you want to understand the current state of the theory.