Well, you don't really need anything to start recording audiobooks other than a good reader, microphone, software to record and edit on, and an editor who can put it all together in a consisten fashion.
However, there are rights for each book - especially if you're going to sell them. I would suggest contacting the pubishers directly and see what their policies are.
What are your goals for this?
I did some work for a few months editing audio for audiobooks, medical journals, educational books, etc. It was pretty tedious to be honest, but it paid 🙂