This book was one of the best damned books I have ever read. It's the best introduction to Skepticism I have ever read.
And then, if you really want to get the old juices flowing, read "Letters from the Earth" by Mark Twain, at least the first half of it. This is not the Twain of "Tom Sawyer" and "Huck Finn". This is a much darker, much angrier Twain. He skewers Man's ideas about God, Religion,and his own place in the Universe. He tears apart the Old Testament, and raises a lot of common sense questions regarding The Flood, how the Israelites dealt with the nations that they defeated (case in point:God orders that no virgins are to be killed when the Canaanites are conquered. How does an army determine who are virgins, and who are not? Unsavory questions not raised in Sunday School...)
Anyway, sorry to hijack the thread. Read Sagan's book. The best point he makes is that the Universe is a wonderful and fascinating place in its own right, why muck it up with belief in stuff like Ramtha, Bigfoot, the Face on Mars, Alien Abductions, The Lost Continent of Atlantis, etc.?