Ian Ker (Professor of Theology, Oxford University) famous for his specialty on John Newman1 has announced a full scale (near 700 page) biography on G. K. Chesterton that will be published in June 2011 by Oxford University Press. If this tome resembles any of Ker's earlier works it should be indispensable for any serious future study on Chesterton and perhaps even become the new standard on him.
1 For example, John Henry Newman. A Biography (Oxford University Press, 2010), ed., The Cambridge Companion to John Henry Newman (Cambridge University Press, 2009), ed., Newman and Truth (Eerdmans, 2009). A lecture given by Ker on Newman can be seen here.