[eschwartz]

Sounds like you are confused about the purpose of Calibre Companion.

CC is meant for organizing and searching for ebooks using the full metadata capacity of calibre itself. It is meant as the catalog and bookshelves of your library, before passing the book to Mantano/other for the actual eboook rendering.

Mantano is a reader app with limited bookshelf+cataloguing capacity. But if you only need that, it should serve well enough.

CC is meant to serve as a layer between calibre and Mantano/other ereader apps, for organizational and general metadata purposes. It can serve wirelessly as a device in calibre, sync read info and do powerful sorting and grouping. It is not meant to be a mere ereader, as there are already apps which do a perfectly fine job of rendering ebooks.