It's a historical leading up to the French Revolution, adapted from the most influential shoujo manga of all time. It has a titanic reputation and it lives up to it.
Let's set some background. In 1972-1973, Riyoko Ikeda wrote a manga that was initially about Marie Antoinette. She's the heroine in the first half of the story, until reader reaction persuaded Ikeda to shift focus on to the supporting character of Oscar Francois de Jarjayes instead. This manga is historically important, became insanely popular and did a number of things for the first time.
Firstly, it had a lead character (Oscar) who's a woman dressed as a man, raised as a man and living a man's life. Women get jealous for her affections. There are precursors to this (e.g. Sapphire in Princess Knight), but what's different about Oscar is that she's one of the strongest characters you've ever seen, anywhere. She's magnificent. If you knew someone like Oscar in real life, you'd run through brick walls for her. She's blurring every gender boundary you can imagine and her feminine side isn't being equated with weakness. Apparently there were Japanese women who'd been watching too much Beru-Bara, had imprinted on Oscar and as a result dumped their fiances for not measuring up.
(For short, it's called Beru-Bara. "Beru" is the first two syllables of "Versailles" if you're Japanese, while "bara" means "rose".)
Secondly, it's a detailed, accurate historical that's not ducking the brutality of the period. Everyone who got guillotined still gets guillotined. You'll see women and children getting gunned down in the street. We see a woman getting branded with a red-hot iron as public punishment, which turns out even uglier than it sounds. More importantly, though, it's bringing alive a passionate, vital period of history in as much detail as a textbook. It feels true and intelligent. (In 2008, Ikeda received France's Ordre national de la Legion d'honneur for writing Beru-Bara.) The Affair of the Diamond Necklace? It really happened and it's here. All the forces that led to popular unrest and the differences between the people and the self-appointed leaders like Robespierre? They're analysed too.
It gives historical context. Everyone already knows about the Reign of Terror (or at least we think we do), but this is much more about the decades leading up to it. Ikeda isn't denying the horror and the bloodshed, but she's also making us understand what made it happen. The old system deserved to fall. Oscar ends up fighting to help the revolution and we're supporting her, even though we know where it's going to end up.
It avoids the trap of seeing history as inevitable. Revolutionaries are fighting for different goals and, in a sense, everyone fails. In the end it's tragedy, as it should be. Don't expect a twinkly fairytale ending.
Ikeda also isn't ducking sex. This was the first manga with a bed scene, although they don't do it in an actual bed. That said, though, it's not a magical Happy Ever After. On the contrary, one of the many powerful things about this story is people discovering their feelings almost too late and/or being separated (either physically or emotionally).
Anyway, the manga's impact was huge. Tomoko and her friends knew more than their history teacher when 18th century France was on the school syllabus. It then got adapted into Takarazuka stage shows and is still, even today, the most famous of them. (It has multiple adaptations since you can't do something this long in a couple of hours, so there's "Oscar", "Oscar and Andre", "Marie and Fersen", etc. Each one chooses different main characters and emphasises a different strand of the story.) There have also been movie versions, including a live-action one by Jacques Demy that doesn't sound very good.
Tomoko knows the manga and Takarazuka versions, but until now she'd never seen the 1979 anime. Her verdict: she prefers the manga. The anime lingers too long on the early, less important court intrigue and skates over some of the meatier stuff (e.g. the trials). Tomoko spent the last ten episodes wondering if the anime would run out of time before reaching the end of the manga. (Admittedly they'd changed directors halfway through.) The anime also cut jokes and a couple of famous lines, while giving Oscar more flashes of femininity, although personally I liked those.
As for me, I was deeply impressed and have no real criticisms. It's a bit slow in some of the early episodes and the art style is simple 1970s shoujo. That's the nearest you'll get. Those aren't problems. Marie-Antoinette is a weird choice for the heroine of the first half, but she's wholehearted, pure and generous. There are a thousand manga heroes like her. It also just so happens that she's a shallow, self-obsessed airhead who's going to make herself and the French royal family despised. The first half of the show is largely court intrigue and almost every character who matters is female and terrifying. Some are noble, but others are poisonous (and usually also real people from history).
It won't take you long to build a list of dukes and nobles you'll be itching to see guillotined. You'd pull the lever yourself.
Meanwhile Oscar cuts through all the bullshit like the Terminator. She's a woman whose not-so-secret weapon is that she's effectively a man in a woman's world. (Her father gave her a male name and raised her as a son.) She has zero tolerance of manipulative, scheming bastards and if she doesn't like you, she'll take direct action. However, at the same time, she's not just an action hero. She loves Marie-Antoinette. She's sensitive to people's hurt feelings. She can lose fights, if she's unlucky or her opponent is tough enough. This just makes her courage all the more admirable.
The second half spends more time in a harder, more down-to-earth world. Oscar has to deal with rough men who reject her out of hand and would cheerfully punch her in the face. She has to fight a gorilla. (He's human, not an actual gorilla, but the resemblance is close.) You'll want to stand up and applaud those thugs' eventual loyalty to her, but boy, was it hard-earned.
One thing that distracted me: Oscar and Andre spar with real swords! It's amazing they haven't died twenty times over during fencing practice.
Weird curiosity: there's an alternative, never-released 24th episode. In one area of Japan, the audience figures were so bad that the show got a different episode 24 that ended the story. It's not a recap or anything. It's original material, written and animated specially... but you won't find it even on any Japanese releases, let alone the recent American DVDs or the Italian ones. (Beru-Bara is huge in Italy, although I think the Italians seem quite keen on Japanese anime in general.)
There's also a Lupin III crossover, in that show's episode 101 ('Versailles Burned in Love'). It even uses the same voice actress for its Oscar. I haven't seen that, though, and I'd point out that Lupin III has a modern setting, with even Maurice Leblanc's original Arsene Lupin being a contemporary of Sherlock Holmes and hence a good century too late for the French Revolution. (The nationality fits, though.)
Sometimes this isn't a subtle show. Ikeda paints her characters in bold strokes, but they're capable of surprising you and the plotting, motivations and relationships are all mature. Sometimes they're even haunting. Bad, bad things happen to our heroes. Oscar in particular is fascinating, with a terrifying sense of honour that I think owes something both to Japanese warrior honour and to the aristocratic French world she belongs to. (Yes, I know she's not Japanese, but she's the heroine of a Japanese story written for a Japanese audience. She's absolutely not a samurai, though, and it's easy to identify huge points of difference between them.) Anyway, she doesn't resent her father and the strange way he brought her up, but instead is grateful to him. She has an awkward relationship with her own femininity. Above all, though, she's the strongest, proudest, bravest person you could imagine. If you had an Oscar on your side, you could change the world.
It's fantastic. Admittedly it takes quite a while to build up to that level, but it's never less than good and great swathes of it are very impressive. It earned its reputation.