The Dark Tower: A Concordance is a supplemental compendium of information compiled by Robin Furth, pertaining to Stephen King's Dark Tower series. The book was initially published in two volumes. Volume I was released on 29 July 2003, covering information contained in The Gunslinger, The Drawing of the Three, The Waste Lands and Wizard and Glass, prior to the publication of the final three Dark Tower novels. Volume II was released on 15 March 2005, covering information contained in Wolves of the Calla, Song of Susannah, and The Dark Tower, following the publication of the final novel in the series. A Complete Concordance was released in paperback on 5 December 2006, and later in hardcover on 31 May 2008.