If you’re hoping to get your writing published, sooner or later you’re going to need to write a query letter....
Why do I want an agent?
Literary agents are essentially somewhere between the guardian angels and the mercenaries of the publishing world. They guide you through your career, bring your work directly to the people who matter, fight the contractual battles so you can spend more time on writing and promotion, and make sure you end up with the best possible deals.
The biggest benefit to having an agent is that they can get your manuscript out of the slush pile. An experienced agent has contacts in the publishing industry, and knows who publishes what, and what they're interested in. While to us mere mortals, the publishing industry behind a wall, an agent knows that Paul from Penguin Random House loves literary writing with a distinct voice, and that Bob from Pan Macmillan is a sucker for manuscripts set in the 1920s with snarky male characters.