Bakemonogatari: AA++
Nisemonogatari: A
So first let me say that Bakemonogatari is pretty much my favorite series of all time, right now. Nisemonogatari is the 'sequel' series, and aired earlier this year. There's going to be a prequel, a movie, called Kizumonogatari released later this year.
The titles are all portmanteaus of the world 'monogatari' which means 'story.' 'Bakemono' means ghost or monster, Nisemono means a fake or an imposter, and Kizumono means 'damaged goods'. If I had to anglicize them, "GhoStory" and "ImpoStory" come fairly easily, though I don't know what to do with Kizumonogatari.
Like most series which I recommend highly, my primary way of recommending Bakemonogatari is to just say "Watch it."
However, Bakemonogatari isn't an S rank, for very specific reasons: it's extraordinarily dialogue-heavy, it's rather perverted, it revolves deeply around japanese mythology, language and symbolism, it's much darker than it looks on the surface and to really get everything out of it it requires a thorough analysis of actions vs words: most of the characters lie or are mistaken, and it is only occasionally pointed out directly that they were lying or wrong in retrospect, it is simply shown that they were wrong or inaccurate.
This makes it the kind of series that you have to let yourself get involved in to fully appreciate. However, the characters are flavorful, the art is absolutely stunning and the writing is clever, it's not difficult to get yourself wrapped up in it.
In short, if you're like me, you'll absolutely adore this series.
Nisemonogatari is overall weaker than the original series, I feel, but is still very good, as it expands inter-character relationships as well as providing substantial character development and further explaining certain characters' history and even more quiet, disturbing implications.
