@The-inkspiller ooh, another hist-fic writer, nice! What periods do you gravitate toward? And combining historical and science fiction could be awesome. I don’t have a head for science, myself, but I admire people who not only understand it but can make it enjoyable to read about. I suppose everyone read the Ender’s Game series before I did (finished last week), but that’s science fiction which I could get into — in large part because that genre offers lots of potential for good ethical dilemmas and this series did not shy away from that. It was philosophical as much as scientific.
(By the way, should you ever want book recommendations to help keep you from forgetting to read. . . I am here to help.)
On the subject of darkness in fiction, especially books by Christian authours: if the ray of light in the end is stuffed in because your audience or category expects it, and not because it’s natural to the story, that’s as much of a problem as if it isn’t there at all — it will ring false that way, and have the opposite of the intended effect (at least with discerning readers; I do know of some who will tolerate any amount of trash as long as it’s got a “Christian message” tacked on). As far as dark tone and content go, apart from that: what authours or books do you admire, and what’s the darkness like there and how do they handle it? If they are truly masterful at their trade, they’ll be able to go into the kinds of blurry areas which take a lot of discernment and expose the issues for what they are. Have you read the Space Trilogy by Lewis? That Hideous Strength, the last book, is the kind of book I will not read before bed (and this is the kid who at eight years old read The Return of the King and went to bed in the middle of the battle before Minas Tirith, and had no nightmares whatsoever (greatly to the surprise and relief of her parents, I’m sure)). There’s all kinds of evil in it, some incarnate, some as bad ideas spreading around, some as evil powers. The good does win in the end, though it would be quite a stretch to say the good guys are uniformly good — they’re flawed and human and some of them very nearly give in. Ancestral Shadows, by Russell Kirk (the famous Conservative, for those of you who know of his nonfiction) is a book of ghost stories as creepy as anything you might expect in that category — ghosts looking for revenge, ghosts + witchcraft, but always the evil is defeated and the good — even at great cost and when you had no guarantee the good guys would have the strength of character to pull through — always wins. (Some of the ghosts are good guys, sent to exact justice from the still-enfleshed bad guys, which is a nice twist, I think, on the usual ghost story.) Also not a book I’d read right before bed. Still a good book.
When it comes to “good” characters, that is “they’re on the side of right but as far as personal qualities go, they’re different from the bad guys only in the ends for which they fight, not the means they use”, you might well question whether they are good guys at all, if they act that way consistently. Generally a bad guy will have some redeeming qualities, like fidelity to a wife (and did you know Hitler was a vegetarian? Had a moral objection to eating animals), though even human villains sometimes kill the last speck of their conscience (“We all have our flaws,” the Duke said, “and mine is being wicked.”). And the best and noblest people I know all struggle with sin. (I mean, original sin, we still have to live with its effects even after conversion.) But good and evil, the absolute standards by which we judge acts, will not change. So try aligning your characters with the moral framework of your story’s universe, and see where they stand. A good book will raise questions in the reader’s mind about what makes an act or a human good or evil. “The bad guy was going to bomb the city, full of noncombatants and women and children, and the good guys said that was horrible and mustn’t happen — we’ve got to save our families’ lives, and all these innocents — so we’re going to bomb the city he’s in, to prevent that from happening, despite the fact that it’s got women and children in it too. Wait, what?” But at the end of the day the book won’t justify evil acts (the end does not justify the means, never has, never will).
Have you read Tolkien’s On Fairy Stories? A lot of what he says is applicable to more than fairy stories, and it’s one of the things I recommend to every writer, because it’s Tolkien explaining why he looks at writing the way he does, and it’s hard to go wrong with that. It’s available for free online, so no excuses. . .