I love conspiracy theories. Any historian who denies doing so is a liar. The search for new ways to look at established facts is the raison d’être of historical research.

Alas, historians can only pursue this passion so far before they start to lose credibility as experts in their field. We’re shackled by the evidence.

Writers of fiction don’t face as many impediments in this regard. They can invent new evidence. Invent new witnesses. They’re free to let their imaginations run wild.

And there’s clearly an ample audience for the stories they come up with. In historical circles, it’s well-known that many presidents of the USA have been Freemasons. Couple that fact with rumors of hidden treasure, and you’ve got a blockbuster movie starring Nicholas Cage. Mix together Gnostics, Templars and kooky European secret societies, and you’ve got Holy Blood, Holy Grail, a 1982 work of popular history that argues that Jesus’ offspring are alive and well today. As history, the book has gotten little respect. But, fictionalized by Dan Brown, it’s become a best-seller and then a movie. (By the way, the authors of Holy Blood, Holy Grail sued Dan Brown for plagiarism…which kind of implies that they knew all along that they were writing fiction, not history.)

Today, the market’s flooded with fiction mixing conspiracy theories together with historical mysteries. How does the discerning reader choose from the wide selection?

Umberto Eco’s Foucault’s Pendulum is the best—the very best—fictionalization of the conspiracy theories surrounding the Knights Templar, a militarized Church order that was exterminated in the fourteenth century. Depending on who you talk to, the Templars were just an ordinary Church order—fighting so-called heretics and saving innocents—or they were travelling to the New World (well-before any other Europeans) and safeguarding the Holy Grail. Oh, and they might have been worshipping Satan. The debate over just what they were up to and the reasons for their extermination remains lively, even today. But Eco (who recently passed away) was at an advantage when it came to explaining all of this. From the kabbalah to obscure occult societies, he simply knew what he was talking about. He actually was a semiologist, the expert in symbolism that Tom Hanks is playing in all of those Dan Brown movies. Eco was the real deal, and it shows. Foucault’s Pendulum (which is set in the twentieth century) weaves together an elaborate tapestry of interconnecting clues and red herrings, challenging not only everything we think we know about what happened to the Templars, but also our reasons for being so very intrigued by these conspiracy theories in the first place.

All of this being said, it’s profoundly disappointing to get to the meat of a conspiracy theory behind a novel, only to find out that this theory is predicated on utter nonsense. (For instance, I recently read a book in which the conspiracy only made sense if you attributed anachronistic Reformation-era ideas to early Christians.) A good historical mystery writer will let his imagination run wild within the bounds of what’s credible. Like Mulder from The X-Files, “I want to believe,” but that doesn’t mean that an author shouldn’t have to work for my faith. Because Eco was so learned on the subjects he was discussing, he managed to craft a story that was credible even as it stretched the established facts. The conspiracy theory behind Foucault’s Pendulum is all the more delightful for being so very plausible. (Most of my knowledge on secret societies and the occult comes from looking up all of Eco’s references.)

Likewise, the conspiracy theory in Oliver Pötzsch’s Ludwig Conspiracy isn’t all that bad. It poses an alternative explanation for the death of Ludwig II, the so-called “fairy king” of Bavaria who constructed the castle that’s the inspiration for the Disney logo. Pötzsch’s conspiracy is entirely plausible. Moreover, he provides a series of intriguing puzzles for the main character to unravel, with messages in secret ciphers. Being something of a fan of cryptology, I think that Pötzsch’s explanation of the Vigenère cipher is a little weak, but otherwise, he does a good job of knitting the process of cryptanalysis together with the narrative as a whole. I think that a clever reader (not me) has a fighting chance of solving some of the ciphers before the main character does, but the solutions aren’t so obvious that the reader will be bored.

The Ludwig Conspiracy excels on one other important point. My #1 pet peeve when it comes to this genre is probably the all-too-common tendency of failing to make other countries and other times sound as if they’re actually “Other.” I don’t mean that I want an author to peddle racist stereotypes. I mean that a book set in another country and/or in another time period should sound and look different from what’s happening right here and now. It shouldn’t sound or look like what I hear and see every day out on the street. Otherwise, the author’s not just wasting my time, he’s erasing difference, in a move that could be interpreted as offensive. Pötzsch has something of an advantage in this area, being a European writing in a language other than English (I read a translation). Though I would’ve appreciated a few more descriptions to really envision a few of the scenes, Pötzsch’s modern European setting seems sufficiently different to me, as a reader in the USA. Pötzsch is also to be commended for making passages that were supposedly written over a century ago sound as if they were in fact over a hundred years old. While the language in these passages would have sounded more authentic if it was a bit denser, Pötzsch has his fictional translator claim that he’s translating the text into modern idioms. That one detail shows just how much Pötzsch thought about his use of language and the past. The effort’s greatly appreciated.

Unlike the two books I’ve discussed so far, Charles Palliser’s The Unburied is actually set in the past (in Victorian England to be precise). Palliser has carefully crafted every line to sound authentic. And if you think that geeking out over that makes me sound a nerd, hold your horses: Palliser’s main character is a historian who learns things by reading books. Yep, the main character comes across a series of manuscripts and figures out the truth behind a medieval king’s political machinations by reading one text against the other. The Unburied provides the best use of this particular motif—textual analysis—that I’ve ever read. Palliser raises our hopes by making us think that we know what happened, only to bring out another manuscript, like a rabbit out of a top hat, to destroy all of our expectations. In the process, Palliser makes something that we shouldn’t care about at all—a long-dead king and his dalliance with power—seem incredibly important and personal. While I didn’t quite understand all of the references to the Church of England and arcane university structure (a chart or glossary would’ve been helpful; the list of characters doesn’t quite cut it), that’s a minor complaint. It’s a great book…and I haven’t even mentioned that the main character is doing all of this while trying to unravel a murder mystery against a backdrop of treacherous academic intrigue.

The other books on my list of the best in historical fiction observe the rules set out above: they provide a plausible conspiracy/mystery, a suitably complicated puzzle that nevertheless gives the reader a fair chance of solving it, successfully “Others” the other (without descending into offensive stereotypes), and/or dives into the intellectual and tactile thrills of textual analysis itself.

Elizabeth Kostova’s The Historian has its characters traipsing across Europe in an attempt to track down the final resting place of Dracula. There are relatively exotic locales (that are, for the most part, sufficiently different), mysterious disappearing books, hard-to-access libraries (which of course just makes the reader want to get inside them), and peculiar legends, all of this culminating in a heady aura of learned speculation that makes a real geek’s toes tingle. In my opinion, the author’s flirtation with the supernatural goes too far at one point—she asks the reader to believe a bit more than is necessary—but you can just ignore those pages.

Iain Pears’ An Instance of the Fingerpost is a Rashomon-like series of fairly authentic-sounding first person narratives, all revolving around a murder in 17th century England. Pears stumbles when it comes to distinguishing the voices from one another, but his use of cryptology sets a geek’s heart aflutter, while his manipulation of varying viewpoints is simultaneously brilliant and infuriating—infuriating, because the reader becomes so entrenched in each version of events that it’s maddening to realize that no one perspective may be wholly correct. (Fair warning: As someone who likes to identify with a narrator/main character, I have to tell you that some of the points-of-views are difficult to read, in part because they’re not anachronistic.)

Laurie King’s Sherlock Holmes series (the best installments of which are The Beekeeper’s Apprentice, A Monstrous Regiment of Women and A Garment of Shadows) offers superb intrigue and mystery while immersing readers in another time and place, again without stooping to stereotypes. King’s version of Sherlock Holmes is so pleasing that, if I had my way, I’d keep her version and ditch the rest, including Doyle’s.

But if I had to have another Holmes, I would take the one in Dan Simmons’ The Fifth Heart, where Holmes teams up with Henry James (yes, that Henry James) to solve a murder mystery. Both The Fifth Heart and Simmon’s The Abominable, which pits spies against climbers in a 1920s bid to climb Everest, offer compelling puzzles and authentic visions of the past, complete with exotic locales, all while avoiding those dreaded stereotypes.

From the Knights Templar to the Yeti, the 10 books on my list provide enough conspiracy theories, mysteries, puzzles, and antiquated dialogue to satisfy anyone’s yearning for learned revisionist history. And hopefully I’ve given you 10 more books to add to your bookshelves…just in time for the holidays, too.