jane, the sony readers all show up as usb mass storage devices (ie. "usb mode") to computers. so, if you want to just drag and drop your non-drm epubs over to the reader, you can. there's no intermediary software required, and unlike the nook, you can drag it to anywhere on the reader (for instance, you can make your own folders).
if you want to use software, you can use calibre, ade or sony reader library. whichever you like better. the only reason to use the sony reader library is if you want to purchase books from the sony reader store or if you want to use the sync functionality in the software.
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