Self-publishing is always an option, but if an author self-publishes a book, they will probably not be able to get an agent to represent the same book at a later date. There can be exceptions -- if a self-published book has really good sales, a traditional publisher may be willing to produce a second edition. That's rare.
If an author decides to self-publish (or send a proposal to an agent),
Jane Friedman is a respected expert on many aspects of publishing. She did a recent article on finding a literary agent. It’s excellent.
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