Here is what I have:
When you enter book details you see something like this:
If you tap on the small button next to Read: you see a variant of this dialog. In this case because the current value is None (empty) the dialog lets you set it to Yes or No.
If the value is Yes" then you see this dialog.
Recall that I can put only three buttons across the bottom, which is why the button labels change. I think that changing the labels so I can have a cancel button is better than having "Yes", "No", and "None" buttons where "Cancel" is tapping the current value.