From the Instructions:
4.1. Loading Audio Files (Music, Podcasts, Audiobooks)
You can transfer music, playlists, podcasts, or audiobooks from your computer to the player
using the drag-and-drop method or using music management software such as Windows
Media® Player. Specific audiobook files from Audible.com require Audible Manager to
transfer to your player.
I’ve never tried an audiblebook, I assume the process is similar to using Overdrive, where you have to transfer the audiobooks to the Fuze+ using the Overdrive console. Because they are DRM protected, you can’t just drag them across and drop them onto the Fuze.
As far as I know, audiblebooks should go into the Audible folder on your Fuze+. If the Audible Manager is like the Overdrive Console, you can select the folder you want to transfer to once it has deteted your Fuze+.
Audiobooks in other formats should be placed straight into the Podcasts folder on your Fuze+, (not the Audiobooks folder), they will show up in a Books folder on the Fuze’s top level menu. If they are not DRM protected, you can drag and drop them from your computer to the Podcasts folder.