The additional post-General Theory material falls into three broad classes. The first class, largely consisting of Keynes-Robertson correspondence, is supplementary to that already published in that it fills gaps in the material in Volume XIV. The second relates to the correction Keynes published to the General Theory when Simon Kuznets pointed out some errors in Keynes's use of statistics that Kuznets had generated. The third is correspondence relating to various aspects of the General Theory which was not previously available.

With the exception of one letter, the additional Robertson material relates to 1937–8. The exceptional letter, written on board the Cunard liner Georgic while Robertson was travelling to America, precedes the Keynes letter printed on p. 87 of Volume XIV.

From a letter from D. H. ROBERTSON, 28 September 1936

(II) I've spent a lot of time this summer on the said book [The General Theory], It's no use pretending I like it much better, or that I don't agree more or less with most of the Prof.'s review, including the first section. I've tried to set down some notes on some parts of the book which may see the light in the QJE or elsewhere. I think it would be a mistake to attempt to discuss them before they are published, if they are going to be. Whether afterwards you will feel that the sort of tabu which has arisen between us can profitably be removed, I don't know.