Here’s the advice I offered, which is generic for anyone in the same situation:
Your photography book will undoubtedly be beautiful and a joy to have and hold. Just like a thousand other photography books, most of which you can find on the remainder table at your local Barnes & Noble. (Being on the remainder table means that the publisher took a bath on the book and sold the bulk of the printing to a remainder specialist at ten cents on the dollar or less.)
There are lots of great books of all kinds that never succeed in the market—that never see the light of day, for that matter. As publishers have tightened their belts over the last several years, they have become extremely demanding in their acquisition process, and the one thing they all insist on now is that the author have what they call platform. Having platform means that the author is already a known public personage in some context. That doesn’t mean you have to be a television celebrity or even a frequent guest on talk shows. It may mean you are on the lecture circuit or that you are well known in your field.
In your case as an artist, what it means is that your first book should be published by the museum that organizes your first touring show and should be assembled and written by the curator. That book, selling in museum shops, will be your ticket to attracting a publisher for your own book later. But right now, put your energy into getting yourself shown in galleries and getting yourself known nationally or internationally in the art world. Work toward the show, and the book will follow.
Now I say this even though my principal income derives from providing services to self-publishing authors, and I believe in self-publishing. If you feel you can sell the book yourself—at showings and lectures and fairs—in quantities that make self-publishing a paying proposition, that’s fine. I’ll be glad to help. But if you really want a mainstream publisher to take you seriously, you have to become famous first. Get yourself noticed.
If you’re already famous, then never mind all the above. Getting an agent should be straightforward.