The Big Time by Fritz Leiber. Ace paperback 1961, 129 pages. Remarkably good condition for its age. It contains a 1971 stamp from Edinburgh's Bobby's Bookshop, offering to buy it back for 8p. (The shop still exists, though they've moved further down the street, and they now specialise in gay lit, erotica etc.)
Hugo-winning novel with an ambitious time-travel plot.

Crooked Little Vein - Warren Ellis - William Morrow Hardback 2007 280pp
Ellis's chilling first novel.

Far Out by Damon Knight Corgi paperback 1963, 221 pages. Rather brown with age, but still in good readable condition.
13 excellent SF stories from the 1950s, mostly published in Galaxy and ASF, including at least one Hugo winner.

Monkey Planet by Pierre Boulle. Penguin Paperback 1979. Condition Battered, foxed but intact and very readable
The origin of The Planet of the Apes

The Water Knife by Paulo Bacigalupi. Orbit paperback 2015. (1st UK paperback edition) 452 pages plus appendix. One careful reader.
Gritty near-future sf set in USA. When the water runs out...

Swords of Mars by Edgar Rice Burroughs. Four Square Paperback 1966. Condition very good.
One of the later episodes of the John Carter epic, first published in 1934.

Some Remarks by Neal Stephenson. Atlantic Books Paperback 2012. Condition as new.
Nineteen essays by the noted sf author, from 1993 to 2012.

Hellflower - George O. Smith - Mayflower Dell Paperback 1964 192pp
Drugs and Crime in the Solar System. Interestingly, the book is dedicated to Dona. Dona was ASF editor John W. Campbell's ex-wife, with whom Smith ran off and married. Thereafter, his stories never appeared in ASF.

Memory of Earth - Orson Scott Card - Legend large format Paperback 1992 175pp
The first volume of his Homecoming series.

Bill, the Galactic Hero - Penguin Science Fiction Paperback 1969 294pp. Very good condition.
A typical satitirical look at future war from the author of Starship Troopers.

Slow Man by J.M.Coetzee - Vintage BooksPaperback 2006 263pp
Troubling tale from a Nobel prize winner

Myst - The Book of Atrus - Hardback, 288 pages. 1st edition. Mint.
The fantasy back story for the Myst adventure games.

The Reproductive System - John Sladek - Mayflower Paperback 1970
Somewhat satirical story about the system that ate the world. Well-written.

The Night Watch by Sergei Lukyanenko. Arrow Books 2007. Paperback. Good condition.
Volume One of the Night Watch Trilogy.

Now Wait for Last Year - Philip K. Dick - McFadden Books Paperback 1968 224pp
Another screwball PKD novel.

The Grotesque by Patrick McGrath. Penguin Paperback 1990. Good condition.
Sinister, mysterious, modern gothic drama.

The Time of Infinity edited by August Derleth. Consul Books Paperback 1951. Old, foxed, but intact.
Short stories by A.E.van Vogt, Fletcher Pratt, Murray Leinster, Theodore Sturgeon and others

The History of the World in 10½ Chapters by Julian Barnes. Picador paperback 1990. 373 pages. Good Condition.
Satirical tale, based around a stowaway on Noah's Ark.