This script will change the file type of the selected AAC tracks--which you have previously made bookmarkable yourself with the script Make Bookmarkable--to "M4A" and file extensions to ".m4a" making them UN-bookmarkable. When used with iTunes 7 or later, each track is deleted and re-added so that it will be removed from the Audiobooks Library. Ratings, play count, last played date, skip count, and skipped date are preserved.
Perhaps Also of Interest...
downloaded 29m 30s ago
Change selected tracks' Start Time or Stop Time by user-entered seconds
downloaded 41m 16s ago
Move selected playlists to a new or existing folder
downloaded 46m 46s ago
Re-locate files of selected tracks to new folder, preserve track meta-data
downloaded 56m 40s ago
Copy files of tracks to selected folder
downloaded 1h 0m 25s ago
Exports and then re-imports selected tracks' artwork
downloaded 1h 17m 22s ago
Remove iTunes tracks disassociated from files