Are they DRM (digital rights management) books?
If so, have you authorized the Mac with the same Adobe ID as you authorized the PC and aquired the books?
If not, I suggest using the far superior free software Calibre ( http://calibre-ebook.com/ )
Will it even let you ask about the books on the Mac?
Right click and 'item info', or menu/File/Item Info, or ctrl-I on PC, probably cmd-I on Mac?
Now that you mention it, that's odd when I installed it on the PC it asked me to authorize the computer as soon as I installed the software which I did.
I don't actually remember if the MAC version asked me to authorize or not?
Thanks for the assistance. I will check if it is authorized when I go back in the next few days and report back.
It just seemed odd that I am able to add it from outside of the program.
Just an update. I was just at the site, and I took a look at the software and the mac was not authorized. I authorized the Mac and the books are now able to be added to the library.
Thanks for for the assistance.