Professor Walls's books include The Problem of Pluralism: Recovering United Methodist Identity; Hell: The Logic of Damnation; C.S. Lewis and Francis Schaeffer: Lessons for a New Century from the Most Influential Apologists of Our Time (with Scott R. Burson); Heaven: The Logic of Eternal Joy; Why I Am not a Calvinist (with Joseph R. Dongell); C. S. Lewis as Philosopher (edited with David J. Baggett and Gary R. Habermas); The Chronicles of Narnia and Philosophy (edited with Gregory Bassham); The Oxford Handbook of Eschatology; and Basketball and Philosophy (edited with Gregory Bassham).

Professor Walls has been an Elder in the United Methodist Church (West Ohio Conference), John Wesley Fellow, a member of the Society of Christian Philosophers and Dulles Colloquium of the Institute on Religion and Public Life, and Senior Speaking Fellow for the Morris Institute for Human Values.