Please ensure that your e-reader is authorized with same credentials as your pc.
If yes, then please try to transfer the book itself.
yes, it is. what do you mean for "transfer the book itself"?
The acsm file is not the book, it is a ticket to get the book. I sometimes get library books online, here is what I do.
1. Start ADE on the computer
2. Go to library website and find the book I want to download.
3. Click on the download link
4. In windows 7 a box opens asking whether I want to open( or run) or save the acsm file
5. Click open/run and ADE downloads the book into the "Library"
6. Transfer the book (epub file) to the reader.