It will not be read. These days, most publishers who still accept unsolicited manuscripts also allow multiple submissions. They just want to be told. Make your submission status very clear in your cover letter. A query letter is what you send to see if there is interest in your project.
Most publishers require a query for a non-fiction project or novel.
It should present your project succinctly, much like the preview you read on the inside of a book jacket, along with brief information about your publishing experience, if any. If the publisher requests sample chapters with your query, send the first pages, not your favorite parts. If they ask for chapter outlines, keep them simple. A cover letter is what you include with your manuscript and should not be more than one page, if that long. Do not include a resume unless it is a non-fiction project and your resume reflects your expertise in the subject you are writing about.