Hubs, Can you please clear up why should I use MarkAble? Why can't I just use a free CD Ripper software (like Exact Audio Copy or CDex) instead?

When choosing a bitrate for your audiobook you should take into account whether it has musical illustration or not. Also bitrate choice depends on a format you use. Low bitrate OGG and WMA sound much better than MP3 of the same bitrate. OGG

I've just opened a free audiobook from AudioBookForFree.Com. It is a 22kHz Mono 24kbps audiobook. That's way enough for me.
Although a friend of mine prefers to encode AudioBooks' CDs to 128kbps 44khz Stereo MP3.
If your iPod supports OGG format, I suggest you to use it for your audioboooks instead of MP3. However I see no reason to convert mp3 files to ogg .

Also I prefer to have small files 'coz it's much easier to navigate.