I consider in the rest of the review, that you saw Bakemonogatari firstly.
As his prequel, Nisemonogatari follow the supernatural life of Koyomi, fighting every kind of ghosts and spirits. The story principally focuses on his two young sisters, known as the 'Fire Sisters' who want to bring the justice in which they believe. The new thing here, is that, after Oshino Meme's leaving, Koyomi will meet other antities' 'experts', who are radically different from Meme. The first one, named Kaiki, is an impostor only interested in making money on the backs of students, and the second one is a woman fighting against immortal demons.
The strong point of the story, as Bakemonogatari, is the supernatural part. People being possessed by spirits is not an over-used theme in anime's world, anyway this one developped it perfectly, with amazing plot.
While mixing comedy and fan service is something rather common for an anime, you'll never imagine that this can be done so well in this show. Some said that it ruined the series, but for me, it adds something that made me love the serie much more. Of course, you should know that ecchi scene are between Koyomi and his sisters, so it can disturb at first.
If you saw Bakemonogatari, you should of familiar with the graphism. It's the same under-developped but no less amazing art. This is such a dangerous thing to be so unique. I have to admit that the first time I saw Bakemonogatari, I thought about dropping the anime. Lucky me, I gave a chance to it. This is really well orchestrated.
Every characters remain to be the same. While Senjougahara and Hanekawa are relegated to supportings roles, Koyomi's sisters and, for the happiness of the viewer, Shinobu get main roles. I really think this is one of the huge lack of Bakemonogatari, but in Nisemonogatari, Shinobu 'the donut's lover' will help Koyomi to fight for his principles.
Interactions between them are, as in Bakemonogatari (if not more), often meaningless, and even sometimes it doesn't result something that can make the story to progress. But this is sooooo pleasurable. Once again, Nisemonogatari used a dangerous development, that can bore, so amazingly that it does just the opposite : it catch the viewer. This is a huge feat.
My enjoyment was at his best, from the beginning, to the end. For a supernatural, mystery and comedy lover I am, this show is the perfect masterpiece. The universe is unique, the art is incredibly sursprising and the characters are very endearing. I really think it can be called a masterpiece, since it mix so many unique things perfectly.
