The choice of copy text for this edition is the first edition published in London in three volumes on 22 October 1886 by Macmillan, in a printing run of 750 copies. That same month Macmillan printed a one-volume edition of 3,000 copies, published in New York on 2 November 1886 (the first Macmillan office in the US had been opened by George Edward Brett in 1869), and in London the following August 1887 (E&L 75–6). For a detailed explanation of the genesis and publication history of the novel, see the opening pages of the Introduction (pp. xxv–xxxix).

The Princess Casamassima is one of James's few fictions for which a holograph manuscript is known to have survived (hereafter MS: see Figure 1 for its opening page). The others are Confidence, The Europeans, and a number of tales (for details see Supino 390–3). A substantial proportion of the manuscript James produced for serialization in the AM was presented to Harvard by the T. B. Aldrich Memorial Trustees and is lodged along with other papers of Aldrich's in the Houghton Library, Harvard (MS Am 1237.5.1). Chapters 1–36 and 39–40 are contained in five bound volumes. The MS of Chapter 38 (74 ‘slips’) is housed in a separate box folder; it was presented to the Providence Public Library, RI, by Daniel Berkeley Updike, and later acquired by the Houghton Library. Chapter 37 is missing, as are the final seven Chapters 41–47.

In principle James sought to number the slips consecutively. The contents of the Houghton volumes are as follows:

Vol. I (Chs. 1–9), slips 1–334

Vol. II (Chs. 10–15), slips 335–633

Vol. III (Chs. 16–23), slips 634–1102

Vol. IV (Chs. 24–32), slips 1103–1207 and 1–147

Vol. V (Chs. 33–40), slips 1–409, less Ch. 37 (missing, slips 153–208). Ch. 38 (slips 209–81) is contained in a separate box-folder.