If you have a Kindle:
You can order from Amazon.com, and have it downloaded to your device.
If you have a Nook:
You can order from Barnes and Noble and have it downloaded to your device.
If you have another e-reader that uses epub format: (Such as Sony)
You may order from a number of sources, including Barnes and Noble, Christianbook.com*, and Bookstrand. Download the file to your computer, and then load it to your e-reader using your USB cable.
* For some reason, Christianbook is now saying GF&M will be released on the 15th of December. Not sure what is going on there, but will keep you posted.
If you want to read from a computer or other device:
Kindle format: If you would like to download a free Kindle reading app for your computer or other device, check availability here: Kindle Reading Apps. Then order from Amazon.
Epub format: You may already have an epub reader on your computer or other device, but if you don't, you can download a free Nook reading app from Barnes and Noble. Then order an epub version from one of the sellers listed above.
PDF format: You can also purchase Gold, Frankincense, and Murder in PDF (Adobe Acrobat) format from Bookstrand and Pelican Book Group. PDF files can be read on most computers. If you need a PDF reader, you can download one for your particular operating system from Adobe.
If you have any questions, leave them in the comments. I'll help if I'm able!