The experience of knowing further truths and gaining more awareness of the divine.
We are all enlightened beings, but some choose to ignore the higher reality, or are lost. With enlightenment, the new found divine awareness is so enthralling that individuals are often unaware they were once living in a dream world. There is a conscious awareness of the connection to being part of the universal creator.
Enlightenment does not make an individual intelligent or wise. All too often, they find themselves as a minority in a community of self-serving people. For this reason, humility and self love is a real virtue with enlightenment as it assists those to survive.
Enlightenment is humorously referred to as lightening-up!
Books:
For a study in instantaneous enlightenment concepts, read "The Lazy Man's Guide to Enlightenment".