One word of warning, if any of your audiobook files are longer than 4 hours you may find you have trouble playing them on your iPod (if they are encoded using the ACC format)
I'm not sure at what point the problem occurs, but your iPod reaches a point in the audiobook that is just past the four hour mark, the iPod may start skipping to the end of the file, loosing your bookmark. This usually happens when you start playing the audiobook after putting it down for a while.
It got so bad that I re-encoded all of my audiobooks into MP3 format, which is a pain as iTunes is no longer able to class them as audiobooks. But at least I can listen to them without loosing my place.