Work-around for 1000-book Dropbox API limit...
Earlier in this thread I pointed out that I was having a problem due to the limitation of 1000 books seen by Marvin in DropBox due to the limitation of the DropBox API. Dragging and dropping or using the web browser to get the books into Marvin seemed infeasible because a calibre library in DropBox has each author in a separate folder and each book in a subfolder.
I worked round this by having Calibre save all books in my library as .epubs in a single folder. Then it is easy to use Windows to drag and drop all 1000 files into Marvin via itunes. There is a link to a tutorial on this in the Marvin webpage FAQ - it is not intuitive.
It took 10 minutes to get the files onto the iPad and it took a clean install of Marvin 20 minutes to refresh the library, but that was all unattended time. With all my books in Marvin, I can now add books as I go along easily using Marvin to browse 'newest' in Calibre.