There is some confusion regarding the Mac and the Sony Reader.
Some people are confused, thinking it's necessary to use Adobe Digital Editions to transfer eBooks to the Reader from the Mac.
No. Do not use Adobe Digital Editions. Use the Sony eBook Library software exclusively.
See this screensnap of About Sony eBook Library:
Click = big
See the red highlighting? This means the Sony eBook Library software now takes over the functions of Adobe Digital Editions. While it's probably still necessary to have ADE installed -- for Adobe DRM authorization -- ADE should not be used to transfer eBooks to the Reader. Only the Sony eBook Library software should be used for that.
Mac owners, feel free to chime in with Comments.
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