Nokia Readers and Calibre

I use Calibre (brilliant software and I have donated) with my Kobo and it works seamlessly, no problem

But I want to transfer to my Nokia 920 with Windows 8.1. The books transfer, not problem and I can see them in the Books folder when connected to my PC. But I cannot find a reader that will find books loaded on the device. Nokia Reader and Freda can happily download from OneDrive but that seems pointless if the book is already on the phone. There is no app to browse the folders on the device.