Grammatically speaking, the things that were acceptable 100 or more years ago are no longer acceptable. This makes sense because of how much the language has changed. What do you, as a writer, do to set a good tone and feel that would set your work apart from a novel set in a more modern setting?
Well, I'm not sure the language has changed significantly since 1909. Since 1609, more so. Still, there are definite cadences and rhythms to languages from different times. To evoke a certain period, I think it's important to be familiar with the rhythm of the time. The best way of doing this, I think, is to read works written at that time (if you can). There are certain words, phrases, and syntax choices that distinguish one time period from another.
I have two stories in the works from very different times. Ancient Rome and
ancien regime France. For the one, I try to add in some Latin words for flavor without confusing anyone who doesn't know the word. For the other, a little French exclamation once in a while is in order ("Mon dieu!"). The French story has longer and more complex sentences with more colons, semicolons, and dashes. The tone is lighter, the rhythm bouncier, the words bigger and more pompous. Scenes are short, quick, and entertaining. Almost everything is superficial, so characters rarely look inward. The Roman story is grittier and has shorter, simpler sentences. The diction is simpler and more earthy. Scenes are longer and I get deeper into character's minds. Oh, and the French story is heavy on humor.
What elements do you, as a reader, look for that makes a book feel authentic?
A certain I-don't-know-what. I want little details in the setting, an authentic-feeling rhythm and diction for the dialogue, and an author who is confident and comfortable in the world he/she is writing about.
One more question: Do you think that a book set in Victorian England should have a different tone than one set in ancient Rome? (This might make a good checklist for those of us how are newbs, myself included.)
I think tone has more to do overall with the subject. You could have a very serious or a very frivolous story set in either time. Different time periods do seem to lend themselves to certain tones, though. Dark times, dark tone. When was the last upbeat book you read about the Civil War?