And another list of ten books (well, two of them are actually trilogies) that I think should be included in the 100 books that best represent the Heart & Soul of 20th Century Science Fiction:
1) The Best of Damon Knight by Damon Knight
2) Gateway by Frederick Pohl
3) A Clockwork
by Anthony Burgess Orange
4) Mirrorshades: the Cyberpunk Anthology edited by Bruce Sterling
5) Riverworld and Other Stories by Philip Jose Farmer
6) The Mote in God’s Eye by Larry Niven & Jerry Pournelle
7) The Helliconia Trilogy by Brian W. Aldiss
8) The Drowned World by J.G. Ballard
9) The Uplift Trilogy by David Brin
10) The Best of C.L. Moore edited by Lester Del Rey
And here we have a couple single-author short story collections and an anthology that includes some of the most influential and/or celebrated short stories in the field. Plus there are 2 novels representing the New Wave, by Aldiss and Ballard, a trilogy by a bastion of hard SF, David Brin, a classic space opera by Niven and Pournelle.
Damon Knight was one of the founders of the Science Fiction Writers of America (now the Science Fiction & Fantasy Writers of America) and has long been consider a master of the short story. This collection includes the classic story "To Serve Man," which was made into a famous Twilight Zone episode.
The Heechee Saga is Pohl’s most ambitious SF and a perfect example of mainstream SF done well, starting with the excellent Gateway, which won the Hugo, Nebula, Locus and Campbell awards for best novel when it was originally published.
A Clockwork Orange is probably more influential as a movie than a novel, but since there would be no movie without the novel, here it is, and the novel is worth reading all by itself anyway, especially with regards to its use of language and the infamous "Ludovico Technique."
Mirrorshades is the definitive Cyberpunk anthology featuring the best writers of early fiction in the subgenre.
The collection by Philip Jose Farmer gives us a superb sampling of the best work by one of the most subversive writers in the genre, and features the original "Riverworld" story that served as the basis of his most success series of books.
The Mote in God's Eye best exemplifies the combination of Sense of Wonder with Military SF, and is quite simply a great "page turner" of a novel.
The Helliconia Trilogy (consisting of Helliconia Spring, Helliconia Summer and Helliconia Winter) could be considered the pinnacle of New Wave SF (with a real Sense of Wonder) by a writer who, arguably best represents that movement.
Ballard’s The Drowned World is a classic post-apocalyptic novel written with a New Wave (and a British) sensibility. Honestly, another "catastrophe" novel of his, The Crystal World, could be listed here in its place. A third, The Burning World, now seems prophetic given global warming and the effects of plastic garbage on the oceans. Ballard is considered to be a major influence on the Cyberpunk movement, and is referenced as such in the Foreword to Mirrorshades. His novel, High Rise, is also a classic. He is best known for two novels that were made into movies: Crash (not the one that won the Oscar for Best Picture) and Empire of the Sun.
The Uplift Trilogy is David Brin’s most interesting, and most important contribution to SF (and a top-notch example of Hard SF blended with Space Opera), although The Postman got more attention outside the genre (due to the movie). The trilogy consists of the books Sundiver, Startide Rising and The Uplift War.
The Best of C.L. Moore spotlights the short fiction of another (THE other?) female science fiction writer who rose to prominence in the early half of the 20th Century (along with Leigh Brackett). This collection features the classic novelette, "No Woman Born."