Dropbox is a great way of adding images to Foliobook
We have recently updated our Dropbox code (completely rewritten in June 2017) and are fully committed to supporting Dropbox in future versions of Foliobook.
Currently there is one limitation, only JPEG images can be loaded from Dropbox. To use other formats such as PNG and TIFF you need to import the images via iTunes.
With Dropbox, organise your images anyway you like in Dropbox. Select the import from Dropbox option when in the lightbox and you will be able to connect to your Dropbox account and then add one or all images from a Dropbox folder.
Note that images are 'imported' from Dropbox, i.e. Foliobook makes its own copies. Foliobook does not 'sync' automatically with Dropbox. Our reason for doing this is that we don't think its desirable for an accidental deletion of a file on Dropbox to result in the image being automagically deleted from Foliobook.
TIP : Images loaded from Dropbox use your color profile set in the original file, therefore these images may appear more faithful in colour and tone than images loaded via iTunes