"That his own diseased imagination should have so far deceived him, is strange; but it is stranger still that some of his friends should have given credit to his groundless opinion, when they had such undoubted proofs that it was totally fallacious; though it is by no means surprising that those who wish to depreciate him, should, since his death, have laid hold of this circumstance, and insisted upon it with very unfair aggravation."
— Boswell, James (1740-1795)
See The Life of Samuel Johnson, LL.D. Comprehending an Account of His Studies and Numerous Works, in Chronological Order; a Series of His Epistolary Correspondence and Conversations With Many Eminent Persons; and Various Original Pieces of His Composition, Never Before Published. The Whole Exhibiting a View of Literature and Literary Men in Great-Britain, for Near Half a Century, During Which He Flourished. In Two Volumes. By James Boswell, Esq. 2 vols. (London: Printed by Henry Baldwin, for Charles Dilly, in the Poultry, 1791). <Link to ESTC><Vol. I in ECCO-TCP><Vol. II>
My main reading text is James Boswell, The Life of Johnson, ed. Claude Rawson, (New York: Knopf, 1992). Also reading in David Womersley's Penguin edition, 2008.
First edition in Google Books, <Vol. I><Vol. II>. See also Jack Lynch's online e-text, prepared from the 1904 Oxford edition <Link>.