I just found a piece of advice that seems quite useful for MP3 versions of audiobooks:
There is no need to download or convert to bookmarkable (remember your place in the book where you were there last) mp4 (.4mb) format for i-Pods or i-Phones.
If you don't want to download or convert to 4mb here is what to do if you want your mp3 Audiobook files to be "Bookmarkable". (Look Like Audiobooks)
Open iTunes, click on "File" tab and select "Add Folder to library". Click the mp3 file or files in i-Tunes, choose get info, go to the options tab, tick "Audiobook in Media kind ", and then tick "Remember position" & Skip When Shuffling".