aka and originally "the twenty-seventh day" (michael joseph h/cvr 1956), q.v.
novels of tomorrow series editor clemence dane.
george philips (possibly by then with the new american library) four square books imprint uk p/b first printing, not first uk p/b edition (which was odhams beacon p/b B26 1958)
cover art by josh kirby (uncredited, art signed "kirby")
cover price 2/6
192pp. including titles, indicia etc.