Although I was never a fundamentalist I was once a believer as well and Robert Ingersoll's writings did more to expedite my atheism than any other person or ideology. Ingersoll was my first glimpse into knowing there were in fact others who thought (and doubted) like myself.
Evolution had absolutely NOTHING to do with my decision to drop kick my faith. The creationists should be trying to ban Ingersoll and leave evolution alone :-)
For those unfamiliar -
Robert Ingersoll complete works
Robert Ingersoll Wiki Pages
And I'll leave you with this Ingersoll quote:
"The man who invented the telescope found out more about heaven than the closed eyes of prayer ever discovered. "
I was fascinated with the reading and it got me to thinking, How many authors have really influenced my thoughts on religion. Granted, I never was a believer, coming from liberal academic parents who, like all good liberals, politely declined religious services, but I was interested since I was born with the God Gene and since we lived waaaaay out in the forested mountains in the North Cascades part of Washington State where god is all around.
William Blake gave me my first images to manipulate the concept of religion with The Marriage of Heaven and Hell. Wierd for a kid to read this but my dad was a history professor so that's the kind of stuff we had lying around. Next came Mark Twain's "Letters From the Earth". My all time favorite is the rant from philip wylie called "The Magic Animal".
I love Ken Wilbur's idea that spirit is what we are evolving toward and the 9 insights from the Celestine prophecy were especially illuminating for me when I read them.
Any way, after providing all these links (I have read both bibles, the book of mormon, the bhagavad gita and etc but they are alittle too political for me :), I wonder, what authors have affected your religious thought?