I have worked out a procedure to import audio books into iTunes. Below you will find a link to Automator script which automates the following steps:
1. Convert files to AAC: some older iPods could not remember playback position in MP3 files. For new ones you may want to use this step anyway to adjust bit rate to save space. I am using following import settings in my iTunes:
2. Adjust volume by 30%. Some books are just not loud enough and I could not crank volume any more in my car. So as precaution I always adjust a volume by 30% - it always possible to bring it down while listening.
3. Pre-set equalizer to "Spoken Word"
4. Set options song: "Remember Playback Position" and "Skip When Shuffling". Unset options "Part of a Gapless Album" and "Part of a Compilation".
5. Set Genre to "Audiobooks"
I am using these steps for few years now and very happy with results. Additionally, if your chapter names have numbers at the beggning (e.g. "01. Intrduction", "02. First Chapter") you may want to use this iTunes script to conver them to track numbers.
Now, as promised, an Automator workflow which performs steps 1-5 on a collection of audio files selected in Finder and adds them to iTunes as a new Playlist, called "New Audio Book". Download "Import Audio Book.workflow.zip" and unzip it into "~/Documents/Workflows". Now you can select files, start Automator and run this workflow. Alternatively, you can open it in Automator, choose "Save As Plug-In" menu and select "Finder Plugin" format. After that you can right click on selected files in Finder and select "More->Automator->Import Audio Book" to run this workflow on selected files.