Edit metadata, convert any ebook type to any other format, list the books on your device and transfer books back and forth, act as a catalog, it even comes with a built-in reader...
A ton of stuff, but it cannot integrate with the Sony bookstore, and it is not cloud storage. Although you can use dropbox, calibre and
calibre2opds together to create your own cloud of ebooks, downloadable via the web browser, this is not the same as managing the cloud that your ebookstore links to your device.
However, it should be capable of doing everything you might conceivably do with the Sony Reader software other than the connection to Sony's servers where they store the books you bought from them and storing annotations. There is an annotations plugin at
https://www.mobileread.com/forums/sho....php?p=2413824 but it only imports from Kindle and a couple of iOS apps at the moment. You could always ask the developer to work on Sony Reader support, though. It would store the highlights in a custom metadata field.