The Wild Swan books on the Coronations are a two-part work, one a highly detailed description of their design, liveries and all the minutiae, the other an excellent photographic album and are what I would consider the definitive work on the class. The RCTS book is equally entertaining, has some different angles on the history and work of the class and of course includes the Princess Royal class and 6202. However, as would be expected, some information is duplicated in the later publication.