My all-time fave is Philip K. Dick’s Ubik.
You’d have a hard time arguing that that’s a novel.
If we’re going to insist on the “first science fiction novel” as opposed to the first work of science fiction, we have to consider not just what counts as Science Fiction but also what counts as a Novel.
What about Sir Thomas More’s Utopia?
Does only serious Sci-Fi count? Because my favorite is The Hitchhiker’s Guide to the Galaxy (at least the first four books).
When I finished reading it, I started writing SF seriously. It turned me into a writer, and I’ve had a respectable number of professional publications.
I can’t begin to explain why.
Fave SF novel? Oh, lordy . . .
While in the past I’d have named a title by Heinlein or Asimov, my dickety-third re-reading of their works (while generally pleasurable) don’t bring new insights. But I still glean fresh perspectives every time I go through Dune.
The Three Stigmata of Palmer Eldritch by Philip K. Dick
I don’t really think in ranked favorites, but if I had to *A Fire Upon the Deep *would be right up there for me, too, along with Dan Simmons’s Hyperion Cantos, which I’ll treat as a single title of I want to, damnit!
Agree. Great concept, great storytelling.
If we’re talking short stories, then my vote is for “The Cold Equations”. Chilling.
Then you probably shouldn’t read this thread.
I think Cyrano de Bergerac’s accounts of his voyages to the Moon and the Sun have a prior claim.
32 posts and no Childhood’s End???
I’m going to go against the general tenor and pick “The City and the Stars” by Clarke. I’m not saying it is the best novel, but it is my favorite because Diaspar is almost reasonable as a city a billion years in the future. Plus Clarke seems to have invented video games, based on my last rereading.
But it is a close thing.
Not anywhere close to being science, even the science of the day. I’ll agree with Aldiss and pick Frankenstein as the first.
There is no way I could pick a *favorite *SF novel. Too many variables. But I can name the one that I have re-read the most times: all five of Jack Vance’s Demon Princes novels (which I basically consider one long story).
Favorite science fiction novel, boy, that’s tough, picking just one.
I think that Clarke’s Childhood’s End is oversold, and not really very representative of his works. Ditto for Heinlein’s Stranger in a Strange Land. You want something that shows off the strengths and capabilities of science fiction, and that I like re-reading.
Maybe the best overall choice is Clarke’s Rendezvous with Rama
Coming in a little after that:
The Foundation Trilogy by Asimov (but not the bloated sequels)
Lest Darkness Fall by L. Sprague de Camp
Starship Troopers by Heinlein, despite, or maybe because of, its controversies. And his positive-feedback armored infantry is one of the cleverest bits of well-thought-out imagined technology I’ve seen. After al his description of not only its conception, but the way opeople have taken to it and use it as a casually-accepted piece of their lives, it ought to exist.
I was thinking that too!
Those four are a great HGttG trilogy. 
Five – don’t forget Mostly Harmless.
Some might also add a Sixth, And Another Thing…, but that was written by Eoin Colfer after Adams’ death.
(And, of course, there are the collected original radio scripts, and Og knows what else)
I have to admit that I’m not the huge Douglas Adams fan others are. One of my first introductions to written SF was the work of Robert Sheckley, whose SF humor is more to my taste. I also think he’s one of the most ripped-off SF writers (I swear that the bulk of Total Recall, after the first 15 minutes or so, is lifted from Sheckley’s novel The Status Civilization, right down to the mind-reading mutants and the hero who is his own doppelganger villain), and I couldn’t help noticing how much Hitchhiker’s Guide resembles Sheckley’s Dimension of Miracles, including a meeting with The Man Who Built the Earth and the extreme poet aliens. But Sheckley’s whimsy is not at all Adams’ sense of whimsy, being more the wise-cracking tough-guy type.
There’s a whole genre of utopian/ satirical/ semi-fantasy novels that can be considered “proto-science fiction”. In addition to the ones already cited I’ll add Gulliver’s Travels, Orlando furioso, and Baron Munchausen.