I can't imagine any agent who could sell someone's work any better than the author could themselves. Find a publisher who functions in this genre, send out some proposals and prepare to have a thick skin. The only thing about which every famous author in the world will agree is that they got rejected a bunch of times before they sold anything.
Well, I'm not famous, but my first novel got rejected 15 times before a publisher took it.
A literary agent brings two things to the table. First, a knowledge of the industry, including, often, an existing relationship with the editors involved. The agent will know who's buying, and who's buying *what*.
Second, the agent acts as an initial filter for the editor. The editor may get thousands of submissions a year, and scans through them (briefly) on occasion, or pays readers to work through the slush pile.
When it comes from an agent, that's the equivalent of already having passed through the first-level filter...the agent probably won't send something unless they, themselves, feel it's worth publishing. The agent knows if he keeps sending dreck to a particular editor, the editor will be less likely to pay much attention to his submissions.
The traditional publishing process blew apart with the rise of the word processor. In the old days, an author had to type a manuscript by hand...the ability to do 300+ pages on this basis was the first filter. Then there was only one, precious copy of the manuscript. An author would consult the industry guides, and pick the publisher most-suited to the genre. If the publisher rejected it, the one manuscript came back (via the author's SASE), and the author would send it to the next publisher on the list.
Now? The author whips it out on a word processor, gets a list of ten or twenty publishers, and emails a copy to all of them simultaneously. The editors get flooded...which is one reason an agent helps.
The situation isn't as bad for non-fiction, since the author usually needs certain qualifications outside the ability to write.
Self-publishing is an option, of course, but the main problem there is *marketing*. How do you tell millions of potential readers your book is out there? Most of the time, the only sales you see are to friends. A web page is one thing, but having a book displayed on the Amazon splash page or on a rack at Barnes and Noble is another thing entirely.
Yes, there are success stories, but they're often niche books. And if they *do* catch on, they often get migrated to conventional publication. "The Martian" started out as an e-book, but there probably wouldn't be a Matt Damon movie coming out this year if it hadn't attracted the attention of a traditional-style publisher.
Ron Wanttaja