The eight and ninth jhanas are difficult to discuss because they are so hard to describe in much the same way nibbana is hard to describe. This is because they are such heightened levels of concentration and of the Path itself, that they must be experienced. There is also very little to discuss with the eighth and ninth jhanas, since the perception levels have become so fine and so subtle. You enter the eighth jhana by letting go of the sense of no-thingness and enter a very natural, calm place. In the eighth jhana there is very little recognition of what is happening, but you are also not totally unaware of what is happening. There is such a peaceful state and you have gone beyond the duality of perception nor non-perception that it is easy to be fooled that you have experienced full enlightenment. But there is still more to do.