I e-mailed them, and I got the response I thought I would; however, it never hurts to try and show that there is interest.

Here is what they said:
"Thank you for taking the time to contact us. Unfortunately, due to the Kindle proprietary format, eBooks purchased at Christianbook.com cannot currently be transferred to Kindle devices and that's not likely to change, as that's beyond our control.
Please let us know if you have any further questions. We look forward to our next opportunity to serve you."