Of course, the right book depends a great deal on your friend's personality. Take a roommate I had in college. She wanted to figure out what it was about science fiction that held my attention so, and asked me to let her borrow "Stranger in a Strange Land".

I gave her "Starbridge" by A.C. Crispin. Why?

This was a very quiet girl. Innocent. She changed her clothes in the bathroom because she didn't want anyone to see her getting dressed. Can you imagine her reading "Stranger"?

"Starbridge" worked perfectly. She was shocked, utterly and completely shocked that there could be sex in science fiction. I didn't want to scare her completely off, fun as it might have been, by exposing her to anything more intense than the mild scene in "Starbridge".

And yes, I laughed.

Of course, "Stranger in a Strange Land" is not something I would hand to most people for their first exposure to science fiction. Heinlein may be one of the great authors, but some of his works aren't for the unprepared.

One of the first things to think about is whether to recommend a book that is more science fiction or more fantasy. The two get so intertwined, and which is really better can depend on what your friend is most likely to enjoy.

The first thing to do is go through your own collection. Knowing your friend, which is the most appropriate to hand over? There's probably something.

If nothing comes to mind right away, I recommend starting out by thinking of some of the more popular authors. "Ender's Game" by Orson Scott Card may be a good choice. Same for "Nightfall" by Isaac Asimov.

The thing to consider is what kind of books, movies or television shows your friend likes already. Science fiction novels can have aspects of any other kind of fiction. The friend who loves historical novels may enjoy alternative histories. The romance reader may be more likely to enjoy the fantasy side of science fiction. The technology buff may enjoy hard science fiction.

Make your selection based on what you think your friend would like, unless you want to try to shock them. Many people are surprised to find out that science fiction novels aren't all ray guns, bug eyed monsters and rockets that can make U-turns.