What IS the Supper for?

In the foreword to Malcolm Maclean's The Lord's Supper (Mentor, 2009), Professor Douglas F. Kelly says:

… at times, I am disappointed at being told at communion services what is wrong with non-Presbyterian views, and then there is a ‘full stop’ before the elements are passed out. I wonder, do these ministers have no idea what Scripture actually teaches about how the risen Christ is using the Lord’s Supper to strengthen the bonds of union with himself? I will be surprised if Malcolm Maclean’s new book does not greatly help them get beyond the mere negative critique of defective views, into something beautifully positive and full of life for the congregation of believers, as well as seekers. (p7)