I too have had trouble with the Audiobooks I’ve downloaded through my library online service (both the Ingram and Overdrive download services). More than once the tags have been incorrectly labeled. I currently use a freeware program called MP3Tag (it supports Windows XP | 2003 | Vista | 2008 | 7) to edit the tags on my Audiobook files.
I have found that for the Clip+ to properly show and order the Audiobook I had to edit the following entries in MP3Tag:
Title: The unique name for the track/chapter/file
Album: The name of the audiobook
Track: The number of the track/chapter/file to allow the Clip to play the files in numerical order
Genre: Should be set to “Audiobook” in MP3Tag
Album Artist: The book author (or if one desires, the person who is performing the reading of the book)
It also helps to enable the Ch. Mode on the Clip+ when using Audiobooks that have multiple files. To enable it go to the Settings --> Audiobook Options --> Ch. Mode and set it to “On”. This will allow one to advance to the next/previous audiobook chapter/file (if the audiobook has multiple files) with the I<< and >>I navigation controls/buttons.