If the book you just downloaded wasn't offered for free by the author or the publishing house, you are stealing. Stealing. It's called Piracy, people, and it's wrong. And illegal.
Do not steal from me, or any author.
Every time you download something from a "sharing" site, you are taking part of an author's paycheck. You wouldn't want anyone to do that to you.
Don't do it.
If you do, you're a douche.