I do exactly what you do with my audio book files, but I listen to very little music.
I have an ipod nano.
With the ipod nano (once you have the files in mp3 format) they are:
easy to load onto ipod.
you can make playlists for your "books" and for your music. That's what I do.
The functionality is very good for listening to audiobooks. It always resumes automatically when you turn machine back on. If you advance to another playlist, it also can resume but there is a process in the option menu you must go through to set it to do that, its not automatic.
with the click wheel though, if you lose your place, you can get back to it very easily.
the audiobook tracks do appear on your main list but the best thing to do is to just make folders for your music and for your audiobooks to make them seperate.
I have never had any success with keeping audiobook tracks in the proper order except through itunes and playing on an ipod. WMP and other types of soft-ware screw it up and the WMA compatible players don't get the tracks in the right order. Its alot of trouble to re-record music to get it into MP3 format, but I also like my books faster so I just play them at double speed using WMP and record on Audible. Then they are in MP3 no matter whether I get them from Netlibrary, overdrive or whatever.
The longer we wait the closer we get. What I want and am sure something will be here like it, is a pocket device that is a PDA as well as a music box and a book reader. Maybe even a phone as well!
For books I have been either downloading from the library and running the propriatary file through an audio recorder which will create plain mp3s that will play on anything. I save all the books to my hard drive because I often later want to reread ... relisten. Or I get CD audio books from the library and rip them to my computer. Okay, so I now have all the books in mp3 format. What to do with them?
I have been uploading them through a card reader to a SD card which I use in my Palm Zire 31. If I don't have too many other things to listen to, this works well. But once I put on several podcasts and then a few jazz albums, it becomes cumbersome. The Palm doesn't have the iPod's ability to recall a library. Playlists are difficult to create on the Palm so I listen to 'songs' which are listed in a long string. Not searchable or arangable on the Palm.
So... I don't care that it doesn't play wma or Audiobooks, or what's the other one. All my audio files are encoded to plain mp3s. What I want is a way of listening to books with a bookmark, and then playing my music which might include random selection ONLY of the music. I certainly don't want a random chapter of the book im listening to in among the Duke Ellington and Diana Kroll songs.
I'm sure it's coming. It's so close now we're all looking for our own perfect system and they are developing them as fast as we can type our requests.