Well, the main thing is, that you like writing. Regardless of how many people buy the books. As long as you write because its your "thing", everything is ok. I mean, you don't have to sell books to get some food on the table, do you.
So all what happens on the writing side is kind of a bonus.
May be you also have picked (well, you didn't by choice perhaps) a bad time to become a writer. To sell your romantic novels as traditional paper books may get increasingly difficult, in the times of e-books. In the fact book segment it still is different, if you have the right subject.
There is a YouTuber called Ian McCollum (aka Gun Jesus) who just published a book with great success. Its called - wait for it - "Berthier to Famas - French Army Rifles from 1860 to Present Day". Talking about niche markets...
Its a big hard cover book that costs $85 or so, and yet its almost sold out right at its publishing date. But that is still a book that people put on their shelve, with lots of photos and drawings and all. As a e-book that would be much less appealing and also harder to use as a reference book.
But such books are less "writer friendly", of course. There is not much so room for imagination and artistic freedom, even if the facts are wrapped into a entertaining surrounding, like your book on Indiana.
Yep; as I've always said, a bad day writing is better than a good day doing (almost) anything else. But even though my books are available as both print and e-books, you're right--it's a bad time to become a writer. You'd think being easier to self-publish would be a good thing, but it means more and more competition for what seems like fewer and fewer readers.
And no, I don't have to sell books to put food on the table ... but I'd like to. By which I mean I'd like to both have to do it and be successful at doing it!
My Images of America: Albion and Noble County book is similarly a niche market, like that one ... and it's one of my better sellers. But I had a major publisher behind me, beating the bushes for buyers, and I'd collected some beautiful old historical pictures to go in it. The number of people interested in historical stuff continues to amaze me. I should add that you're right about that, too--it wasn't a writer friendly project. I love history, but I'd rather be writing fiction.