It says file could not be opened because it was either not a supported type or it was damaged. I have already had the file resent and in talking to the American Medical Association (purchased from their site) it appears when I go to open the file it is in Adobe Reader and I do not see an option to move it to Adobe Digital Editions,
I think the book you perchased/downloaded is in pdf format.
Adobe Reader is the default reading program for pdf format.
If you have digital editions installed, then
You can either open the book in digital editions by right clicking on the book and select open with digital editions.
Or you can open Digital Editions directly and add the book to the library and open it.
I hope It helps.