The Reader Library is from Sony. It integrates ADE (that's why you need both installed (if I'm not mistaken) into Sony software. It should work fine for most stores.
However it seems with Fictionwise you need to use ADE directly. To open ADE, you can see if you have an Adobe Digital Editions in your Programs. The Sony software tends to steal the file associations so it might open by default when you double click on and ePub file or open an acsm.file.
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