For an Audiobook, it was necessary to play it as music, and rename the Album for each disk with a prefix, like 01, 02 .. 0N, it could not keep the tracks from mixing otherwise.
Changing default MP3 encoding settings for 256 bit rate
Use the following command in the terminal to see values for lame encoder
gst-inspect-0.10 lame
I've added a bitrate parm in addition to lowering the vbr-quality to 0 from 6 for best quality
My Preferred format setings:
audio/x-raw-int,rate=44100,channels=2 ! lame name=enc mode=0 bitrate=256 vbr-quality=0 ! id3v2mux