Riyoko Ikeda, Rose of Versailles (1 vol. of 5—I actually have the whole series but I'm trying to preserve a little of the suspense for myself by not reading further than I have translated). 

The historical saga of Marie Antoinette and the French Revolution, focusing on Oscar Francois de Jarjayes, a female member of the Royal Guard.  The one thing I admire most about this manga so far is the sheer amount of historical research involved—it includes a bibliography!  The artwork looks a little bit dated, to be honest, but that's entirely understandable given how long ago it was written.  Again, this is a story that shows much potential.  There's a lot of character development in the first volume—you really feel like you know Marie Antoinette, Oscar, and some of the other peripheral characters by the end of it—and it sets the scene of royal ostentation juxtaposed with the extreme poverty of the lower class to set up the conflicts that are coming soon.  The one thing that I must say about Rose of Versailles is that it exerted an undeniable influence on "Utena", which takes the real revolution as metaphor, and also has a way-too-cool-for-words crossdressing heroine.  (Saitou Chiho herself, in an online chat, said that Riyoko Ikeda was one of her favorite mangaka).  It's a must-buy for any manga fan with an interest in the French revolution.