I have one book that I purchased online, and the company seems to allow users to read the book only through their app (which I'm not 100% sure, but the error message below implies it).
However, I could no longer access the account so I could not read it on app. The book data is under
~/Library/ApplicationSupport as PDF file. There is another file with an extension .dat on the same directory.
But when I tried opening the PDF file, the dialog appeared, saying it may be damaged or use a file format that preview doesn't recognize. I tried installing Adobe Acrobat Reader but there appears the same error message.
Is there any way to read the PDF file, possibly on iBooks?