I’m not exactly sure how to write about the new Starz series Outlander. Partly because I’m nervous that I might say the wrong thing and enrage the show’s fervid fan base—yes, a show that hasn’t aired yet can have a rabid following, if it’s based on a beloved book series, anyway. But also because the series, which involves time travel and 18th-century Scottish politics, is so hard to classify.

Is it the steamy bodice-ripper its marketing materials make it out to be? It certainly has the potential to be, but save for some hanky-panky in the first episode, its first six installments are relatively chaste. Is it the Game of Thrones alternative some are calling it? Well, there are castles and swords and stuff, but it’s a simpler, gentler show than that dark, sprawling epic. It’s a little of everything, but not entirely anything. Outlander’s mix of genres and tones is strange, but it’s nonetheless a disarmingly enjoyable series, its various intrigues having the effect of a slow sneak attack. I was bored and confused by the pilot—you may want to turn on the closed captions to help decipher the thick brogues—but by the end of the sixth episode, I was thoroughly, unabashedly hooked.

Here’s the rather bizarre premise: in barely post–W. W. II Britain, a beautiful nurse, Claire (Caitriona Balfe) and her historian husband, Frank (Tobias Menzies), take a romantic, sex-filled vacation to the Scottish Highlands. But after watching a local pagan-ish ritual, Claire touches some kind of enchanted stone and finds herself transported back to 1743, when Stuart-supporting Scotsmen were waging guerrilla war against occupying British forces. Smart, resourceful Claire doesn’t spend too much time freaking out, instead ingratiating herself into the wary Clan Mackenzie, who keep her a well-attended prisoner in cold, muddy Castle Leoch. Claire has an immediate connection with a handsome young clansman named Jamie Fraser (the dashing Sam Heughan, who already has a healthy cult following), but she is, of course, still in love with her husband, who is presumably searching for her in the 1940s. But so far, this show isn’t a tortured romance. It’s more interested in the political machinations of clan and country, which Claire maneuvers like a pro, all the while trying to figure out how to get back to her own time.

She also uses her skills as a field nurse when they come in handy, positioning herself as a healer, met with both awe and nervous skepticism by the relatively primitive locals. So we have lightly simmering romance, time-travel fantasy, politics and rebellion, and, in one episode anyway, medical mystery. It’s an olio of tropes and themes that don’t immediately appear to gel well together, but once you’re lulled by the show’s peculiar rhythms, it all starts to commingle rather nicely. It helps immensely that Balfe is such an appealing actress, possessed of the same iron-willed grace as Jessica Raine, the star of the similarly hued British series Call the Midwife. It’s a particularly British quality, this forcefulness mixed with poise and reserve. At times Claire is maybe a little too coolly competent, given that she’s time-traveled two hundred years and all, but for the most part, Balfe makes Claire a spirited, principled, genuinely heroic heroine. She and Heughan have good chemistry together, but it’s surprising how long the show takes to really address their yearning tension. The show’s restraint is respectable, but I suspect some viewers will get antsy.

Which brings us to the big question about Outlander. Who is this show for, exactly? Obviously fans of the book series will flock to it. The show seems to be pretty faithful to the books, with Claire’s frequent voiceover (as soothing and melancholy as Call the Midwife’s) giving the the story a novelistic feel. I imagine readers will be pleased. But there are few of the epic, violent thrills found in Game of Thrones, and practically none of the graphic sex. Six episodes in, the show has yet to become a true romance. A sad episode all about tax collecting (seriously) is followed by a dark, interior episode whose climax is a long, intense two-hander interrogation scene. The show occasionally flashes back (forward?) to the 1940s, but not consistently, so we go long stretches untethered to Claire’s “real” world. A casual viewer taking a passing look at the show might have no idea that she’s a time traveler. There’s not one, or even two, genres to easily label the show with, which is, qualitatively, a good thing. But its thematic variation may oddly mean that Outlander is a series with a pretty narrow, or at least specific, demographic. This is maybe Starz’s most assured original series to date (there’s an argument to be made for Boss, certainly), and yet I’m not sure it will reach enough people to catch fire.

I hope I’m wrong. Because there’s something deeply likable about this odd series. It has the defiant confidence to own its idiosyncrasies, trusting its audience to be as invested in the workings of clan fealty as we are in the sexual tension between heroine and hunk. The series also doesn’t seem particularly fussed, at least not yet anyway, with explaining how Claire’s incredible journey came to be. Which, in some ways, is the hallmark of engrossing fiction, which assumes it has us rapt near immediately, and thus doesn’t need to bother with exposition. It took me a couple of episodes to fall under Outlander’s particular spell, to stop chafing against its refusal to define itself. But once I did, I found myself falling pretty hard. It won’t be everyone’s cup of tea, but it’s undeniably a strong, unique brew.