I’m not sure. Best I can say is to try sending from Calibre again, or check the format and see if it works with your reader. If you are transferring to iBooks, ePub or PDF work.

If all else fails, add the book to Dropbox or even email it to yourself as an attachment. Then you can choose the option to Open in iBooks and it will transfer it in. If that doesn’t work, there is definitely something wrong with the file.