I’m going back and forth between researching and writing, on my new novel draft. I don’t follow any sort of organized plan so far as historical research reading goes. I don’t finish all my research reading before I start to write, or even after I’ve finished writing. I don’t read everything there is to read; sometimes I skim for what’s relevant or might be relevant. Sometimes I decide I don’t need a particular source, and return it to the library, mostly unread.
Even a writer who attempts to research everything they’re writing about won’t be able accomplish it, because some of what they want to know simply won’t be available; even if, like me, your interest is in the early twentieth century rather than, say, 1300s Europe. I’ve long since accepted that even if “everything” exists for me to find, I don’t want to commit the time to find it. At some point, I have to write the story.
For example, I could go hunt up the insurance maps for a particular city, for a particular span of years. I could find the exact house where it would be possible for my characters to live. I could then get the phone book and find out who really lived there. But do I need to do that? Will it add to the realistic feel of the story if #317 housed a bookseller in both real life and in my novel? I suspect that sort of resonance would have meaning for absolutely no-one besides the person who did the research. And aside from that, if you go that far, when do you stop? A real person lived there! Do you have to copy their furniture for your character? Their ultimate fate? That path leads to mimesis rather than storytelling. At that point, you might as well be writing a biography.
That isn’t to say I wouldn’t like to know everything about my chosen time period. I would! I began writing stories set in and around World War One because I was interested in the time period, and was already reading about it. I still read about it, all sorts of books that may or may not be relevant to what I am writing. I also fantasize about the invention of some sort of time travel camera where I could spy on real events of the past without the risk of being smushed by a runaway wagon or something.
Facts are important. Significant details are very, very important to worldbuilding; they can give a level of reality to fiction because they are, well, real. The trick is finding those significant details in the first place, the ones that will stand out, and using them in ways that will resonate for the reader. You won’t always recognize the facts when you see them, and sometimes you’ll have no idea that one of those facts will show up in your research reading. Accepting serendipity is sometimes much more important that slavish attempts at historical accuracy that serve no story purpose.
And then there are the facts you cannot find, or do not have the time or resources to find, even with the internet. That’s when it’s time to MSU – Make Sh*t Up. The trick there is to MSU thoughtfully, using what you already know and and trying as hard as you can to make your S feel real. Sometimes, this will fail horribly. Sometimes, no one will ever notice except you.
I guess what I’m saying is that I don’t make an idol out of Historical Accuracy. It just isn’t possible, and though I do try, I know that I will always fail, no matter what. So I try not to freak out if I can’t find out the price of persimmons in 1911 in Manchester, England, or even if you could buy persimmons at all.