Dianne, it's important to tell a little about yourself too. You need to give yourself credibility. Example for you: the fact that you've hosted a web site/forum for however many years, advocate for battered women, do speaking engagements, etc.

Think of your query as a advertisement for you.

Don't be modest. Pour it on.

You need to convince the agent/editor that your book must exist. Tell what sets it apart from others on the same topic.