Lowdown: Sagan's version of The God Delusion.
Carl Sagan has been dead for 10 years now. This does not, however, stop him from publishing new books: The Varieties of Scientific Experience is a result of his wife's (Ann Druyan) editing of lectures Sagan gave during the eighties to a forum in Scotland which invites people of distinguished persona to lecture them on natural theology. While I doubt most of us, including the Sagan admirer in me, would categorize Sagan as a a professional in the filed of theology, the result of his lectures is so good I would gladly have him appointed as the pope.
Natural theology, according to both Sagan and your average English dictionary, is to do with the studying of god through natural phenomena - as in, according to Sagan's interpretation, thorough science and through critical observations and the conducting of repeatable experiments in peer reviewed processes. Naturally, this is a bit different to the methodology most of our religions come from, which usually is more to do with revelation and blind faith rather than verifiable facts.
Sagan uses the opportunity provided to him through these lectures to marvel at god's work: the book starts with an overview of just how big and how varied the world we live in is, and just how small and narrow our scope of looking at it is; a fact that becomes obvious once one looks at our extremely limited and species biased religions. Sagan continues to explore his scientific based approach and compare it with what religion offers us, and without really trying to do so he ends up constantly mocking our religions. The result ends up raising very similar issues to the ones raised in Richard Dawkins' The God Delusion, yet there are some significant differences between the books: while Dawkins' book is an all out attack at religion, Sagan is exploring, not attacking, and just happens to conclude that our religions are lacking. Sagan is also much more philosophical, as evident by him exploring his subjects and speculating on issues using his expertise in astronomy (as opposed to Dawkins, who as an evolutionary biologist tends to explore the same ideas using findings from his field of research): Sagan discusses what we can learn from other objects in our solar system regarding the evolution of life on earth and regarding the way we treat this gift of life that was handed over to us with, say, nuclear weapons and global warming. He moves on towards further speculation through his research into the subject of UFO's and through discussions on a topic he was very passionate about, the search for extra terrestrial life and in particular intelligent life. While those may sound exotic and unrelated to religion, Sagan uses such subjects to explore around religious concepts and question them.
Eventually, while he marvels at the work of god, he is very much in agreement with Dawkins on the issue of Western religions. The example that I took from the book involved Sagan asking why, when we buy a used car, we take such great care in testing to see that it is any good, while when we take on a system of rules and morales that govern the way we conduct our lives from start to finish we're fine with taking others' words for it, no questions asked - and most often, questions are better off not asked. If you ask Sagan, the religious admirer who wants to delve further and study god's work should not bother wasting his/her time with the familiar religions; the studying of math, for example, would be much better.
Given that the book is lecture manuscript based, it is written almost as a dialog, and as such it is very clear and extremely easy to follow despite the heavy subjects it digests. Overall I would say the book is just about perfect in the way it handles its subject matter; better yet, it is simply a pleasure to read Sagan as he analyzes his matter. The one fallacy the book does have is in its introduction, written by Ann Druyan: it reads as rather apologetic, as if trying to tell the reader that despite Sagan saying a lot of nasty things about our religions, he is "old testament". Don't ask me what being old testament means, but it's fairly clear the introduction was written in order to help the chemistry of the book with the current state of mind in America - a place where religious zeal seems to be on the rise.
Overall: I gave The God Delusion 6 stars out of 5, which is the wrong thing to do by many's accounts, especially as Sagan's version is just as good a read. Still, I will give the Sagan book just 5, as The God Delusion is a much more conclusive book that also has the potential to be a more important book, historically. But don't let The God Delusion being the good book that it is stir you away from the Varieties of Scientific Experience.