I am aware that iBooks has not made EDEN, book 3 of the Providence series, available. I have checked Smashwords, who provides my books to Apple, and it is indeed available to them, and it has been available to them since May 1st. I’m unsure why they have yet to make it available to you. Please contact iBooks to let them know you want to read EDEN.
Then, if you do not wish to wait, I suggest downloading the free Kindle app, and purchasing EDEN from Amazon. Even if you can’t wait, I ask that you please be sure to contact iBooks, as this problem will not be resolved unless they are aware.