My theory of evolution is that Darwin was adopted.
-comedian Steven Wright
I've been a big fan of Michael Shermer ever since a buddy of mine loaned me his copy of How We Believe. Shermer blew me away. Since then I've seen him speak in person three times and enjoyed it each time. His latest book, Why Darwin Matters is a very good book. In a polite, decent and respectful manner, he shows the reader compelling and impressive scientific evidence for the evolutionary process, while at the same time pointing out the various weaknesses of creationism and its new and improved variant Intelligent Design. By showing how "multiple lines of evidence" from biology, physics, astronomy, paleontology, anthropology and other areas prove that life is the natural result of a slow, incremental and therefore evolutionary process..
Shermer also takes a critical look at the Intelligent Design community, mentioning that all of the more notable ID scientists with the exception of one are evangelical Christians, (the exception being Jonathan Wells, who is a Moonie). According to Shermer, the Discovery Institute in Seattle is funded not by the scientific community but by conservative groups, thereby making the Institute an agent for social change and not scientific inquiry. Lastly, such groups promote their agenda not by doing objective research or publishing articles in peer-review journals but through the courts and the political process.
Readers who are turned off by the militant tone of "atheist chic" writers such as Richard Dawkins will probably find Shermer a bit more to their liking. I would highly recommend his How We Believe as well as his Why People Believe Weird Things.