As the newcentury began, Doyle's history of the Boer War continued to attract critical attention. In a June 1901 profile of Doyle, a reviewer for Literature reported that the book, then in its twelfth edition, was “enormously successful” (June 8, 1901, 480). It was important enough to warrant reviews in the Athenaeum (November 23, 1901) and The Dial (February 1, 1901). The London Quarterly Review deemed it “the finest book yet published on the Boer War” and a heartening endorsement of the British fighting spirit (March 1901, 391). The Edinburgh Review, however, dismissed Doyle's account as a statement of the obvious about a region and a people (the Boers) already familiar to the British reading public (February 1901, 267–268). Doyle's revised and expanded editions of his History of the Boer War also drew responses, almost all focused on the historical accuracy and political wisdom of his assessment of the conflict. Typically, however, there was little agreement on the book's merits. The London Quarterly Review praised it as a display of “true patriotism and enlightened imperialism” (January 1903, 163). Yet W. D. MacGregor, whose three-part rebuttal offers an alternative view of historical events leading up to the war, challenges Doyle's support for the imperialist aims of the British government (Westminster Review 157 [1902], 477–489; 157 [1902], 597–611; 158 [1902], 28–41).

The Boer War was merely one of a number of matters of public interest about which Doyle wrote during the next thirty years. During the first decade of the 1900s he was in the public eye expressing his opinion on matters such as British diplomatic and military policy, military strategy, free trade and tariffs, divorce, and the need to produce motor cars in the United Kingdom. He ran for parliament in 1900 and 1906—though he lost both elections. He spent considerable time, effort, and personal resources trying to set right what he considered a miscarriage of justice in the cases of George Edalji, a mixed-race young man convicted of animal mutilation, and Oscar Slater, a convicted murderer. These efforts had the effect of changing the public's view of him; he was regarded not simply as a writer but as a man of “affairs,” as The Spectator dubbed him in a 1904 review.