Having trouble downloading my free gift

I signed up today and was taken to the screen so I could download my free gift. I chose the Disaster E-Book, and as the download screen hadn’t started, I clicked for a manual download. It soon finished downloading, and I went to close the screen, to find that it hadn’t downloaded fully. When I tried to open the file, it came up with an error screen.

Can anyone tell me how to make sure this file downloads fully and what could have possibly gone wrong.