What @eschwartz said

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And as for the inconsistencies between what Calibre does by default and the the "no sharing + ASIN fix" combo, they lie in the fact that Calibre uses a "fake" uuid, while you're expected to use a valid ASIN for the fix (i.e., social media sharing *requires* a valid ASIN pointing to the right book).
I seem to recall that Calibre *might* try to use an existing ASIN if it's set properly in the (Calibre) metadata, which may save you a step, but I might very well have been dreaming that one up

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