Eli Bendersky's website Secondary title: "A personal view of the search for god".
This book wasn't actually written by Sagan, but rather edited from his lectures by Ann Druyan (his wife and co-author). The lectures were given at the Gifford Lectures on Natural Theology of 1985 at the university of Glasgow in Scotland - a very prestigious set of lectures that once featured Heisenberg, Bohr and Whitehead, among others.
Druyan spiced up Sagan's lectures by including modern astronomical color photos taken of distant stars and galaxies (photos that were unavalaible to Sagan in 1985, before the Hubble telescope was launched). With the many illustrations in it, the book is quite short and can be read in a few hours. It summarizes the lectures and provides a sample of Q&A; between Sagan and the audience in the end.
There's not much new about Sagan's views here, especially for hard-core fans like me who've read most of his books before. However, I don't think that in other books Sagan speaks of religion so directly - his way of thinking is clear (for example in "Demon haunted world"), but here he addresses the questions of God's existence more directly.
So the book is good if you want a pretty good sample of what scientists think about religion (in a much milder way than Dawkins says it). It's also a must if you're a fan of Sagan's writing, of course.