I convert audio books to MP3s and listen to them on the standard Music Player application that comes with the Android OS (Motorola Droid). The file name of the MP3s is the format "Artist - Book - Track #", with leading zeroes for low track numbers. All the MP3's have ID3 v2 headers filled in.
Recently I've found that when the number of tracks is over 100 the music player fails to sort the tracks correctly - they seem to be in almost random order, or groups of tracks are sorted correctly, but the groups do not appear in the right order.
I was able to fix this problem by making sure that the ID3 v2 Track # field is filled in. It seems that without this, the music player doesn't sort the tracks correctly.
Just passing on the helpful information. I will re-post if I find this doesn't always solve the problem. Does anyone know more about what the sort criteria are? Can anyone explain how tracks are sorted when the track # is blank?