Science fiction... Hmm
Ok well I'll start with my favourite:
Peter F. Hamilton is an excellent hard sci-fi writer. His books are quite long and in depth, it'll keep you busy for a while. Be warned though, his books aren't exactly light reading. The plots of many of his trilogies are pretty complex, lots of things happening at once and all that.
His 'lightest' trilogy is also his first. The'Greg Mandel trilogy' is about a retired soldier come-private dectective. However, Greg was part of the mindstar brigade, a project by the military to produce psyhic soldiers.
Greg lives in england, where the country is recovering from the tyrannical rule of the People's Socialist Party.
I won't give away the plot, but that's the background of the story. This trilogy combines classic detective novels and science fiction. So if you like mystery this is pretty good.
Mindstar Rising is the first book.
His second trilogy is "The Night's Dawn Trilogy." This is an excellent series of books, the first Peter Hamilton book I read was 'The Reality Dysfunction,' the first book in the trilogy.
The thig i love about Night's dawn is that there are almost elements of fantasy in it, yet it is undisuptably hard science fiction. Everything is explained quite well and the plot thickens with each book to come to an amazing climax.
The background to this is that humanity is spread across the stars, but is split into two races. Adamist and Edenist. Adamist are what you expect, spacefaring humans. The crews of ships have implants and genetic traits that were implanted into them to help them cope with zero-G
Then there are Edenists. These humans have similar zero-G genetic traits, but what really sets them apart is "Affinity" and 'bitek.' this ability is like a limited telepathy that lets them communitcate with others who have the affinity genes and with the bio-technology that makes up almost all of the Edenist systems.
However, there is soemthing more in this world, something darker than human nature, yet born of it.
I highly reccomend this. I hope that finding out what the Reality dysfunction is will be as awesome for you as it was for me.
Next are the Commonweath Saga (2 huge books) and the following Void Trilogy. Set in the same universe. The Commonweath saga tells the story of a world where humans live for centuries by a regeneration technology that allows their body to be renwed to early 20s. Travel between worlds is facilitated by a vast wormhole network; travel is by train through the wormholes making it nearly instantaneous. Then a scientist discovers something very strange about a pair of stars...
The Void Trilogy takes place about 1200 years after the Commonwealth Saga. I highly reccomend reading the saga first though, since due to the lifespan of the characters, many events and even characters from the Commonwealth Saga are referenced by or are in the Void Trilogy. The focus of this is on the Void, a massive thing that threatens the entire galaxy, and humans are about to make it worse.
I also highly reccomend Ender's game and the rest od the Ender series by Orson Scott card.
Then there's the classics. Isaac Asimov's Foundation saga. This is a must read for any science fiction lover. The events are concerned with 'Foundation' a bastion built to guard against the end of the Galactic empire. Over the decades, the Foundation faces many challenges, both from inside and from outside, including the Empire which spawned it.