If God Were a Space Alien: A Different Kind of Atheism by James Hamilton
Approx. 31,280 words.
Published on February 25, 2009.
This short book presents a variety of thought experiments designed to expose people to some rational ways of thinking about their god or gods. An attempt to distinguish a visit from god from a visit by space aliens is just a light-hearted introduction to more serious material. The underlying theme is that whatever way you have of knowing about god is evidence, and can be explored as such.