Christopher G. Moore was at Left Coast Crime 2009.
Christopher Moore was not.
The book dealer who brought Christopher Moore's books to sell to conference attendees didn't know the difference, or thought that conference attendees didn't. No excuse, really. The list of conference attendees included a hot link to Christopher G. Moore's Web site where 'tis obvious he writes a very different tale than Christopher not-G Moore.
Imagine your surprise if you'd purchased a Christopher Moore book from the book dealer and, having reached the head of the "have Christopher Moore sign your book" line, you discovered the Christopher Moore (Christopher G. Moore) in front of you looked nothing like the author photo on the (Christopher Moore) book you had in hand.
Here's the basic difference 'twixt the two:
"Think Dashiell Hammett in Bangkok." —San Francisco Chronicle (Christopher G. Moore)
"Moore's storytelling style is reminiscent of Vonnegut and Douglas Adams." — Philadelphia Inquirer (Christopher Moore)
Now you know ...
Buy either. Buy both. Different reads. Very different reads. Both worth reading.