I'm using the list from the Book Haven site. This seemed like the most reasonable example to me. Other online lists include books like Lord of the Rings, or present the list entries in a questionable order. The Book Haven list is of course also open to debate, but given my years (decades!) reading throughout the genre, it seemed like the most reasonable example.
Defining what science fiction is can be tricky. Is C.S. Lewis's "Space Trilogy" science fiction? Is Infinite Jest? Is A Canticle for Leibowitz? At the end of the day, labels like "science fiction" are always open to debate - no more or less so than labels used for types of music, or food, or cultures.
There is also the question as to what "best-selling" means. Given that there are more science fiction readers alive now than ever before, should we assign Orson Scott Card precedence over Frederick Pohl? Or should we adjust the term "best-selling" to account for percentages of the market at any given time? Surely the influence of certain authors counts for something, and just because Robert Heinlein's sold more books than Jules Verne doesn't mean that he's influenced more people.
1. "Stranger in a Strange Land" by Robert A. Heinlein
I can't stand Robert Heinlein. Believe me, I've tried. He has to be one of the most condescending authors ever, and aside from the usual "space aliens and rocketships" tropes, I've found very little substance in any of his books.
It seems to me that only those who read Heinlein in their youth would be able to develop a fondness for this author. Anyone else - anyone first exposed to much better science fiction - would probably avoid him.
2. "Dune" by Frank Herbert
The first novel is fairly overrated, although it was definitely revolutionary for its time. Some of the later entries in the series are excellent. I'm a big fan of both Dune Messiah and God Emperor of Dune. Heretics of Dune is also great, but Dune and Children of Dune are ponderous in the extreme. And Chapterhouse Dune? Simply terrible.
If you've read this blog for a while, you're probably aware of my fondness for Frank Herbert. This is partly due to nostalgia, partly due to his origins in the Pacific Northwest, and partly due to the more interesting entries in his bibliography.
If you've already read through the Dune books, I highly recommend The Godmakers, Soul Catcher, the Eyes of Heisenberg, and Hellstrom's Hive. Many of the ideas first presented in these non-Dune books were later folded into the Dune series, and a reading of these four novels will enhance your enjoyment of Herbert's best-known series.
One of the strangest things about Frank Herbert is that his WORST novel, The White Plague, seems to be everywhere.
3. "2001: A Space Odyssey" by Arthur C. Clarke
A lot of this book was hammered out in the presence of Stanley Kubrick, while they were putting together the screenplay for the film. For this reason I don't think you can give Clarke ALL the credit for 2001, though he certainly did most of the heavy lifting.
Despite writing a few crappy books, Clarke refrained from writing any as crappy as the latter entries into Asimov's "I, Robot" series. He was, generally speaking, a better writer than Asimov, and one of the things I appreciate most about Clarke is his succinctness. Some of Asimov's later books really feel like he was grinding out his obligation toward a publisher, whereas Clarke, even at his worst, wrote engaging stories that can still be appreciated today.
The three sequels to 2001 are all good. None of them will blow your mind, but they're all solidly written and very readable. For Clarke at his best, see entry #9 below.
4. "The Hitchhiker's Guide to the Galaxy" by Douglas Adams
If you're wondering why people still worship these books, you'll probably also wonder why people like Monty Python and Doctor Who. They're predicated upon a very British sense of humor, and those with more "American" tastes will be mystified by them.
For my part, I loved all of the books in the series. Life, the Universe and Everything is my favorite, but I thought they were funny right up to the last book.
I haven't read anything else that Douglas Adams has done. My impression is that his other novels aren't quite up to the same level? I could be wrong, but they don't seem to enjoy the same kind of audience.
5. "Fahrenheit 451" by Ray Bradbury
Ray Bradbury always struck me as a writer of "serious fiction" trapped in the body of a sci-fi writer. He'll spend pages waxing poetic over spaceflight, but the stories in which these mini-poems are to be found are all very minimal - little more than outlines.
Is Fahrenheit 451 his best book? I'm not sure. It's certainly the best known. I can remember being unimpressed with it, and both his Martian Chronicles and The Illustrated Man seemed much better at the time.
6. "Do Androids Dream of Electric Sheep?" by Philip K. Dick
Why is this Dick's best-known book? Because Blade Runner. Ridley Scott's ode to AI was adapted from Dick's novella.
In a way this is unfortunate because Dick wrote much better stuff. But then again, I suppose "Do Androids?" is merely an entry point to Dick's catalog, an appetizer if you will, and those seeking true strangeness will find Dick's other books, eventually.
Of all the writers discussed here, PKD (as he is often referred to) is by far the trippiest, and maybe also the best. His stories of time travel, alien intelligences, and alternate timelines continue to exert a powerful influence over the popular imagination, and it's safe to say that modern science fiction would be much, much poorer without him.
If you want to get WEIRD, I suggest spending a week(end) with his VALIS trilogy. Fans of more conventional sci-fi will likely prefer novels such as Martian Time Slip and The Man in the High Castle. Whichever point of entry you chose, it's worth looking over Dick's bibliography beforehand. He wrote a lot of books, and although none of them are really "bad," many of them are very similar.
7. "The Foundation Series" by Isaac Asimov
Isaac Asimov was a smart guy. He also wrote some of the most important books in all of science fiction. I, Robot and the first (published) Foundation book are brilliant, and the only reason these books aren't the source of more films is the fact that they are, for the most part, unfilmable.
Even so, Asimov wrote a lot of crap. His Foundation series goes downhill fast, and his I, Robot series goes downhill even faster. Some of these books contain interesting ideas, but these ideas alone aren't enough reason to struggle through most of his novels.
If you really want to know Isaac Asimov, the best way is through the short stories that made him famous. It's in stories like "Jokester" that Asimov really shines, and I have had ample cause to regret that he gave up short fiction for the more lucrative novel.
8. "Ender's Game" by Orson Scott Card
Before you embrace Orson Scott Card too enthusiastically, be aware that he is 1) a practicing Mormon, 2) believes that homosexuality should be illegal, and 3) believes in "Intelligent Design" (i.e. the Biblical account of creation).
With this said, I don't think you can always hold every author responsible for every ridiculous thing he or she believes. Many famous authors were chauvinists, many were racists, and many others also believed that the Bible should be taken literally on all points. The problem here is that Orson Scott Card is a writer of science fiction, and many (if not all) of the beliefs listed above speak against a scientific understanding of the world. If you're only after "space aliens and rocketships" this is no problem, but if you're after fiction based on sound, scientific conceptions of the cosmos this is definitely an issue.
For what it's worth, I've read both Ender's Game and its sequel, Speaker for the Dead. Ender's Game is a fairly competent effort, though Speaker for the Dead is, in my opinion, bad. I did like Card's take on Iron Man in Ultimate Iron Man, but I can't say that I've bothered to read him since. To put it simply, there are much better writers out there, and Card's belief system hinders his development beyond the established tropes of the genre.
9. "Childhood's End" by Arthur C. Clarke
This book is fantastic. It remains one of the best science fiction novels ever written, and displays a level of prose unmatched by anything Clarke did after. It deserves the praise it has received, and it was written with an economy that few other science fiction writers can match.
10. "Gateway" by Frederick Pohl
It's been SO long since I've read this book that I can't really say much about it. I remember reading this and its sequels when I was in elementary school, but my recall of any Frederick Pohl books is sketchy. Maybe I should read him again?