The query letter has one purpose, and one purpose only: to seduce the agent or editor into reading or requesting your manuscript or proposal. (Anything sent alongside the manuscript or proposal is really a cover letter and doesn’t hold as much weight.)
In other words, the query letter is a sales piece, and it’s quite possible to write one without having written a word of the manuscript. All it requires is a firm grasp of your story premise or book concept.
For some writers, the query will represent a completely different way of thinking about their book—because it means thinking about one’s work as a product to be sold. It helps to have some distance from your work to see its salable qualities.
I recommend your query include these elements, in no particular order:
In its entirety, the query shouldn’t run more than 1 page, single spaced for a novel, or somewhere around 200 to 400 words. I recommend brevity, especially if you lack confidence. Brevity gets you in less trouble. The more you try to explain, the more you’ll squeeze the life out of your story. So: Get in, get out. Nonfiction authors—because they often need to speak to their platform and marketing considerations—may spill onto a second page or go a little longer, up to 700 words or so.
Sometimes a successful query breaks all rules and standards because it’s done in a way that’s charming and reflects something unique about the writer. The real challenge is knowing when your effect is truly charming or in fact annoying, and it’s a tough balance. You want to have some life in the query, but not at the expense of it backfiring and distracting from what it’s there to do: get the agent to request and read the manuscript.
Do not tell an agent or editor to learn more about your book by visiting your website or blog. Rather, follow their submission guidelines and send what they ask for, in the format they prefer. While it’s fine to list your website or blog as part of your contact info or as part of a platform discussion, there’s almost never a reason to tell agents they ought to or must visit your website. Most of them will Google you anyway and check out your online presence to get a sense of how you might be to work with and if you have a meaningful platform.
Some writers are tempted to discuss and post their submissions materials at their site, such as a query, synopsis, book proposal, and/or excerpts. While this isn’t wrong, it’s unlikely to accomplish anything. If an agent/editor stumbles on your site for some reason—due to seeing you on social media or reading your material somewhere—they are very accustomed to proactively reaching out to ask about any books you’re working on. If you put too much information at your site, it could in fact dissuade an agent/editor from contacting you if it’s poor quality or doesn’t put your best foot forward. So, if you do post your submissions materials, do it with exceptional forethought.
First, you have a tough road ahead. Learn why.
If you must query, do not lead off with “I self-published this book and thought you might be interested.” The immediate reaction will be I am not interested in your self-published book. In other words, the fact that you self-published is not a selling point. It is a negative or at best a distraction if you’re addressing someone in the industry. Pitch the success of the work, e.g., “I self-published this book and have sold 50,000 copies so far.”