What goes in a query letter?
A one-page pitch to an agent containing three things: what the book is, who you are, and why you are writing to them specifically. It is a sales document, not a summary.
The structure that works:
A personalised opening. One line establishing why this agent — a book they represent that is comparable, something they said they were looking for, a specific connection. Generic mass queries are recognisable instantly and are treated accordingly.
The metadata. Title, word count, genre and category, and one or two comparable titles. Word count matters more than writers expect — a manuscript substantially outside the expected range for its genre signals inexperience before anything else is read.
Comparable titles should be recent, commercially published, and reasonably successful without being enormous bestsellers. "Like Harry Potter but for adults" reads as naivety; two apt mid-list comparisons read as someone who understands the market.
The pitch — two or three paragraphs. This is the substance. Introduce the protagonist, what they want, what stands in the way, and the choice or stake that drives the book. End on the central question, not the answer.
This is not a synopsis. It should make someone want to read, not explain what happens. Withholding the ending is correct.
A short biography. Relevant publications, competition placings, professional expertise where it bears on the book. If you have none of that, say nothing rather than padding — no credentials is entirely normal for a first novel and is not held against you; inventing significance is.
A brief close, thanking them and noting what is attached.
What sinks queries:
Not following submission guidelines — the most common and most avoidable failure. Guidelines are a test of whether you can follow instructions.
Describing the book's themes or your intentions rather than its story.
Claiming it will appeal to everyone, which signals no understanding of positioning.
Rhetorical questions as an opening.
Querying before the manuscript is finished — for fiction, it must be complete and revised.
Non-fiction differs, using a proposal with chapter outline, market analysis and platform.