It costs less than one lunch, and it belongs next to every monitor that's used for email or blogging. Me? I own three copies: one each at the office desk, home desk, and home easy chair. I'll start keeping one in my car, too, if the rush hour traffic jams get any worse.
Here's the book I'm talking about ...
Excerpt from Chapter IV, Words and Expressions Commonly Misused:
Nauseous. Nauseated.
The first means "sickening to contemplate"; the second means "sick at
the stomach." Do not, therefore, say "I feel nauseous," unless you are
sure you have that effect on others.