London: Printed for W. Strahan; and T. Cadell, 1776-1788. Rare complete first edition set, including the rare first state of volume one, of Gibbon's landmark work of historiography. Quarto, 6 volumes bound in full contemporary mottled calf, with morocco spine labels lettered in gilt, gilt ruling to the spine in six compartments within raised bands, gilt turn-ins, three engraved folding maps by Kitchin of the Western and Eastern Roman Empire and of Constantinople. First edition, first issue of vol. 1 with errata uncorrected, [one of 500 copies], half-titles (that in vol. 1 a tipped-in later facsimile), 3 folding engraved maps, engraved portrait frontispiece after Reynolds and vol. 1 *a4-*b2 (Contents) bound in vol. 2, vol. 1 with later engraved portrait laid down as frontispiece, with all cancels and errata as called for, engraved bookplate, later ink ownership name S. de Giles to rear pastedowns. While the first volume was on the press, Strahan decided to increase the print run from…