Recommend A Good Sci-Fi novel to me.

[trancejeremy]

And while I'm at it, don't forget Alan Dean Foster. He's got a pretty big space opera-ish setting, "Humanx" (even a Gurps supplement for it). (All of his work is pretty good, actually).

http://en.wikipedia.org/wiki/Alan_Dean_Foster

 

[trancejeremy]

And while I'm at it, let me also recommend Kristine Kathryn Rusch's series which I can't remember the name of (and can't remember how to spell her name, actually). But it's science fiction. Apparently mankind in the future ends up signing treaties with all sorts of different alien races, including extradition treatries. However, a lot of the aliens have all sorts of strange laws and punishments. And so humans end up facing lots of horrible penalties. In order to avoid this, groups have sprung up to help hide people who are facing these weird penalties/crimes. But at the same time, people have also sprung up to help find those people who get hidden. Retrieval artists, IIRC. Sort of like a private detective story. Kinda. I liked them anyway.

 

[Rackhir]

The Honor Harrington series by David Weber are good space Opera. Especially the first couple of books like On Basilisk Station.

His Starfire novels, co-written with Steve White are also a great read and are especially good if you like reading about vast fleets of starships blowing the hell out of each other.

 

[Mallus]

I'll second Mike Resnick. Start with Santiago, a space western done long before Joss Whedon cooked up Serenity. Not the most science-y science fiction around, just a great story written with a lot of wit, heart, and humor.

Also consider...

John C. Wright's trilogy that begins with The Golden Age. The title's a bit of pun; it's like Golden Age (1940s-1950s) science fiction for the 21st century, with strong echoes of one of my favorite old SF writers, Cordwainer Smith. The highest praise I can give them is that I loved the books despite hating their politics.

And Ian M. Bank's Culture novels. Particularly Use of Weapons. Just read it.

Lastly, since you've read Delany's Nova, I feel I have to recommend his Dhalgren. It's not space opera, in fact it's only nominally science fiction, and many people find it unreadable. I think it should be considered one of the great works of 20th century literature (it should be on any list that includes works like Gravity's Rainbow.

 

[RaceBannon42]

Altered Carbon by Richard K Morgan a Sci-fi noir book basically a hardbitten future detective story

River of Gods by Ian MacDonald A near future story set in India very good.

 

[WayneLigon]

Darwin's Radio by Greg Bear. One of the best SF novels I've ever read. There is a sequel but Radio is fully self contained.
Jumper, Helm, and Wildside are all excellent stand-alone books from Steven Gould.

 

[sckeener]

China Tom Miéville's Perdido Street Station or The Scar are stand alone-ish. They have a more steampunk feel, but are good books.

 

[Wombat]

A lot of good, wide-ranging suggestions here, sci fi being rather a more broad and hard to categorize section than fantasy.

Might I suggest one utterly out of left field? Richard Garfinkle wrote a book, Celestial Matters, now I believe sadly out of print but available in most used book stores. It is a "hard science" book, but the science in question is Aristotelean; it is sort of about war, but the war is between the Delian League (Greece & its allies) and the Middle Kingdom (China and its allies); it is sort of a space opera, in that the action takes place primarily on a large rock hurtling through the spheres of the planets trying to reach the sphere of the sun. It has some very strange and wonderful characters, too boot.

It is an odd duck of a book, but I enjoyed it thoroughly!

 

[Mark CMG]

One of the classics that some few miss is Canticle for Leibowitz by Walter M. Miller Jr.

 

[Ulrik]

I'' second the recommendations for Niven's books (Ringworld and the Mote in God's Eye especially), Ender's Game, Snowcrash, The Forever War, and especially A Fire Upon the Deep.

Also, Alastair Reynolds has written some excellent hard SF space travel books. For a self-contained novel I'd recommend Chasm City (which I also think is the best of the ones I've read).

Weber's Harrington books are space opera, but they're also very much military SF. If you don't like spaceship battles, stay away - but otherwise Weber is a master of writing spaceship battle scenes!