"I believe that it is my job not only to write books but to have them published. A book is like a child. You have to defend the life of a child."--George Konrád
When trying to interest a publisher or agent in a book, unless otherwise instructed, never send the book first. Always begin with a query letter.
A query letter is a letter that poses a very basic question: do you want what I have to offer? This of course means, do you the editor want what I the writer have just written. Please?
A query letter should not be longer than a page and should outline your book succinctly; it should provide some context for the subject matter of the book; and it should suggest why you are the person to have written this book. Being brief is quite difficult, but it is essential. This is where you would include both your short bio and your abstract, along with some connective tissue--why you are querying this particular publisher, where you got their name, why you think they would be interested, and so on.
DVICE. A little bit goes a long way. Make your points and get out of the letter. An editor sees these queries with great regularity, and likely spends time with them. Grace and clarity are far more impressive than eight pages of bad summary to someone who has read 10 or 20 or more of these in a single day. Either they are interested or they are not. But remember, finding good books is their job. This moment is important to both of you.