I understand the appeal of historical fiction for writers. Historical research allows an escape from present-day drudgery, a chance to delve into another world where your boss is non-existent, the latest pressures of work are far away, and the heart can operate at a slower rate altogether. Stamp collecting, golf, chess, yoga and knitting all do the same thing, I'd imagine.
But if you set your book in a past era, make sure your research is thorough. There's no excuse, say, for having your central character meet Queen Victoria in 1904 when she'd already been dead for three years. Yet that sort of stuff gets written. You don't have to get it right straight away, but you have to allow your manuscript to be checked for blunders and then be prepared to edit accordingly. I'd call that technical editing*, checking that the details in the background stack up properly. If you were writing a crime novel, or a science-based work, you'd surely let an expert run an eye over it. Historical fiction is no different.
You might have researched a period extensively, but a trained historian knows how and where to look to check your details. Get your history right and, like Tolstoy, your novel might one day end up as essential reading for history students. Get something wrong and your readers will end up laughing at you. Because in every field, be it arts or sciences, researchers are known not for their best piece of research but rather for their worst blunder.
* I've written about developmental editing and line editing elsewhere.