I don't know how short you mean, but here are some I think of as shorter.

Hitchhikers Guide to the Galaxy
And Then There Were None (or any Agatha Christie)
Sherlock Holmes compilations
Pride and Prejudice (gateway to Jane!)
To Kill a Mockingbird
Little House books (Laura Ingalls Wilder)
Animal Farm or 1984
Fahrenheit 451
Alex Rider series (sometimes a little violent)
39 Clues series