@senigami said:
Until the Audiobooks section is officially supported I have a working fix for getting Audio Books into Plex that will work on phones and roku as well! Obviously it is not as good as official support but this is probably the best you are going to get for now. It is fast too, only takes a few min to get your book into Plex.Items Needed:
MKVToolNix
Dummy Video Track (custom 10 min blank video) tiny file @ 124 KB
BulkFileChanger (optional)
Audiobook maker like Markable or Chapter and Verse (optional)…
I just tried what you said, man, that’s working great! 
I used the same trick, but I used Windows Movie Maker, but my video file was at least 5x as big as yours and took more than one hour to convert one book with Windows Movie Maker while it only took a few seconds with MKVToolNix 
