Reviewed by John McEwenTHAMES & HUDSON, 352pp £60Tablet bookshop price £54                Tel 01420 592974This generously illustrated book commemorates the 400th anniversary of the death of Domenikos Theotokopoulos, known as El Greco. The author is professor of art history at Madrid’s Universidad Autónoma, the curator of the current exhibition, the largest ever, being held at the Museum of Santa Cruz and in other venues in Toledo through to 14 June.  Additions to a canon earn their scholarly place through new material. Professor Marías’ coup has been the discovery of El Greco’s annotated copy of Vitruvius, consolidated by privileged access to a similarly annotated cop