From the comments on this post:
Question, though: obviously we’re still going to want to include a query to hook the editor/slushpile reader, but most LDS publishers accept unsolicited manuscripts. Do you think getting the query letter perfect [is] less important than when the query is the only thing the agent/editor has?
The query is still your first contact with the editor—and first impressions are a big deal. Therefore, your query (with or without accompanying manuscript) is still very important.
Real life example: My assistant reads all queries first. Good queries = manuscript goes into my Read Now pile. Bad queries = manuscript goes into my Read When I Have Time pile.