#1: Dune (Frank Herbert)
Science Fiction doesn't get significantly better then this. Dune is every Sci-fi aficionado's wet dream. Lots of people claim Dune is Science Fiction's reply to "Lord from the Rings" and that i ought to agree: it sure is. There are many good sci-fi books, but Dune is actually a giant among giants. It is actually a pinnacle of Science Fiction literary achievement. In the event you haven't read Dune, doesn't waste more time. Read it now!
# 2: Starship Troopers (Robert Heinlein)
War is beautiful based on Robert Heinlein. This can be a novel concerning the glorification of war. The premise: space-marines wearing special armor battle vicious alien insect aliens. It is classic "traditional" science fiction at it's best. It's a rip-roaring ride throughout the galaxy that you don't prefer to miss.
#3 : Ender's Game (Orson Scott Card)
This is probably the corner stones of science fiction and one novel that you shouldn't miss. A critique on society, the storyline of a boy who refuses to give up, a battle to avoid wasting the fate of mankind - this science fiction book combines them into one addictive and compelling mix that shouldn't be missed.
#4: Foundation (Isaac Asimov)
This can be undoubtedly on of the finest works of science fiction ever written. When you a fan of science fiction with grandiose and epic storylines, get your hand on this book.
A corollary: Foundation is a series for folks who love grand and complex ideas. Should you be looking for a book heavy in the action but thin on concepts, this most likely are not the novel for you. The strength of the ideas presented would be the focus on this story, not the characterization. Regardless, this is just one of those Buy sci fi book that you only need to read. You might never think of Science Fiction exactly the same way reading the basis series.
#5: Snow Crash (Neal Stephenson)
Part-time hacker and pizza delivery boy and full-time samurai swordsman, meet Hiro Protagonist. Snow Crash is breath taking novel with action and pacing thick enough to drown in. Snow Crash redefined and rejuvenated the Cyberpunk genre. If you need a novel with bucket tons of action, futuristic technologies ala The Matrix, plus the gritty futuristic dystopia with the Blade Runner world, Snow Crash is the perfect recommendation.