Audiobooks

Quick question

I usually buy my audiobooks on CD (or get them from the library)

There was a book I really wanted to listen to that was unavailable in physical form.

So I bought it through iTunes last week and figured that I could just burn it onto a MP3 CD so I could listen to in my car.

I found out that I couldn't burn it.

Is there was way to convert the book so I can put it on a MP3 disc?

Thanks for your help