SF Masterworks is a series of science fiction books published by Orion Publishing Group through it's imprints Millennium and Gollancz. Beginning in 1999 the list is made up of select science-fiction books from as far back as the H.G. Wells. Malcolm Edwards, managing director with Orion, created the list with the goal of bringing important books back into print.
The books are numbered in series publication order, not original publication date, and are highly prized and collected.