[BionicGecko]

Congrats, $103 is an incredible deal!

Personally I always use the send to kindle web interface on the Amazon website to transfer content to my Scribe. USB transfer won’t work if you want to use the pen at all on your books or PDFs. The desktop app seems to have issues with some files, at least the Mac version. Send to kindle via email is limited to the email size supported by your email service (so I think 20 - 25 MB is a practical limit) whereas the file limit on the web interface is 200 MB. As for send to kindle from mobile, I really don’t find a use for it as it would mean transferring the file from Calibre from my desktop PC to the phone first, which is pointless since I can do it directly from my PC.

As for Libby, I only have one account so I might not be of much help here, but from what I gather, each book has its own link to the library it was borrowed from; you don’t really “assign” a Libby account to the Kindle in the same way as you assign your Goodreads account. So I don’t think it would be an issue to add books from different library sources.