Noberto is a retired scientist turned self published author. He wrote and published his book through Amazon's Create Space and wants to expand to Apple iBooks. Leo says that using Create Space means he's stuck with just Amazon, and that really is the biggest place. Getting it on Apple iBooks can be done in a similar fashion. Apple offers iBooks Author for free. Apple will let him do self published works, but the key is to get it in the right format (ePub).
Noberto should check out this FAQ at apple.com about it.