How long it takes to write a book depends on its length.

Some of my ideas were shot down by Lucasfilm because they stepped on territory that has been reserved for the movies. I didn't have a problem with that.

Working within the limitations of the shared world generally made the writing easier, because I didn't have to invent any of the characters or background, which is usually the hardest part.

Science fiction readers probably have the gene for novelty, and seem to enjoy a cascade of invention as much as a writer enjoys providing one.

I've experienced writer's block, but never for more than a few days.

The mass-market paperback, for one, is too expensive.

Even if you only want to write science fiction, you should also read mysteries, poetry, mainstream literature, history, biography, philosophy, and science.