An attempt to list all the castles of England and Wales, this highly scholarly text in two volumes by the late, greatly respected, D. J. Cathcart King is the standard text. It is the prime authority for the lists of castles in this web site. The introductory chapters are a fascinating, if a little difficult to read, discourses on the history of the recording of castles and a paradigm of the castle. The appendix includes a listing and discussion of some of the obscure names of castles recorded in medieval documents but not identified with specific site. A must for the serious scholar though generally inaccessible to the casual castle enthusiast. King was aware that his listing was incomplete and the Gatehouse
web site is an attempt to carry on his work and make it more widely available.
See also Renn, Derek, 1984, 'Review: Castellarium Anglicanum
by D.J. Cathcart King" Medieval Archaeology
Vol. 28 p. 277278 online copy