Actually, unlike majority who have written reviews about Nisekoi, I feel that it is quite a good manga.
If you have watched the anime, and are planning to read the manga now, you should be warned that the start of the manga would shock you. The art is ... meh but after awhile the art work goes to the expected standard i.e. like the anime.
I really like harem manga and anime so the story was great, so it got a 9/10 for story.
The characters are quite good too, there are a wide range of characters.
I enjoyed reading it as I watched the anime first and wanted to know what happened afterwards.
The ending was so sweet that I nearly cried and I have never cried over a manga/ anime.
Overall, to me, this manga was awesome.
However if you have watched the anime, I recommend that you start from the part where the anime ends as it is very boring to reread.