The Thomas Somerville letters are 13 letters bound into a single volume. In his correspondence, addressed to publishers Andrew Strahan and Cadell & Davies in London, Somerville discussed the creation and subsequent publication of his book The History of Great Britain during the Reign of Queen Anne. He wrote 8 letters to Strahan and 5 to Cadell & Davies. Somerville recounted several aspects of his work as a historian; for example, in one 5-page letter to Strahan, he discussed the book in depth, and voiced his "hope for an auspicious reception of the history of the reign of Queen Anne" (October 11, 1795). Somerville also noted the thoroughness of his research, and alluded to the processes of creation that underlie historical authorship: "There is not a publication, foreign or domestic, relative to the history I have prepared, that has not been inspected by me with minute attention. I could easily produce a bulky volume of original papers, but I mean to publish only such of them as are illustrative of the history, or curious on account of the distinguished characters of the authors" (October 11, 1795).
Somerville strove for brevity in his writing and wanted the opportunity to refine his published work in the future. He seemed equally concerned with both the literary quality and the factual content of his work, and wrote Strahan, "I expect to have at least the merit of publishing not a sentence, or perhaps not a word, superfluous" (January 25, 1798). He later reported, "I have been occupied for some time past in the perusal of the Shrewsbury papers, which contain valuable materials upon the subject of my former volume and would enable me to improve it with interesting facts" (October 4, 1798).
Somerville's later correspondence focused more prominently on different aspects of publication, and included several discussions of his subscribers. About marketing methods, he wrote "I am perfectly satisfied with your proposed indulgence concerning the Indian speculation. I must, at the same time, desire you to observe, that I did not mean that all the hundred copies which I commissioned should be placed to the list of my subscribers" (October 18, 1798).