Percy Shelley wrote Alastor in the fall and early winter of 1815 while he and Mary Godwin were living quietly in a cottage at Bishopsgate, one of the eastern entrances to the Great Park of Windsor, in the Thames Valley west of London. He arranged for the printer Samuel Hamilton to produce 250 copies of a volume comprised of Alastor and eleven shorter poems, the copyright for which he offered to the publisher John Murray in early January 1816 (Letters, I, 438-439). After Murray refused Shelley’s offer, the volume was published jointly in February 1816 by Baldwin, Cradock and Joy and Carpenter & Son.
The Alastor volume was no best seller, but by the time of Shelley’s death in 1822 all copies had been sold, and Mary Shelley, who had difficulty obtaining a copy for her own use, reprinted Alastor with Shelley’s Posthumous Poems (1824).
– from the headnote to Alastor in the Norton Critical Edition of Shelley’s Poetry and Prose, ed. Donald H. Reiman and Neil Fraistat, pp. 71-72.
Page facsimiles of the first edition can be found at the archive.org.