The same was true of my second book about my dad's service in WWII. Is there a huge market for this book? No, but the historical photos and documents my dad left behind needed to be placed somewhere that people could enjoy and learn from them and not simply be left in an old cigar box.
My advice is that you need to ask yourself why you are writing the book, and who is your intended audience. Who cares? Once you know that, you can make the decision on whether to go forward or not. I leave you with this extremely funny video about writing a book.