Most new Authors look for literary agents to help them get their book published. These agents work hard at making sure every manuscript is presentable to publishers and will work closely with authors on building their platform.
Literary Agents represent authors to publishers on their behalf. They negotiate royalties and contracts to help authors obtain the most money they can for their manuscript. Agents will help with book proposals and query letters and provide editorial expertise so it will attract publishing editors.
Some literary agencies help with editing, illustrations, and cover art design. Some go as far as helping with marketing your book to the public. Why hire a literary agent? Because they will help you to find a decent publisher, and present your brand to the public, help you establish contacts and explain publishing contracts to you.
Keep in mind that Literary agents charge a commission of 12 to 15 percent from the sale of your book. As an author you must weigh the benefits and decide if a literary agent will help you accomplish your end goal.
Other useful links: http://suite101.com/article/what-does-a-literary-agent-do-a150298