Nisekoi is a romcom harem manga with the catch that the MC Raku, the son of the yakuza boss, has to pretend to date the daughter of the mafia in order to keep the two groups from fighting. Along the way, other girls pop into the circle and all end up falling in love with Raku. The manga is generally very slice of life, with many chapters just representing a single day in the lives of these high schoolers, but each character does end up getting one or two arcs dedicated to them. This is where Nisekoi does so much better than a lot of other harem manga. A lot of the harem manga I've read are largely plot-less or are littered with incoherent plot points that serve no purpose to the overall story or characters. Most of the major plot points in Nisekoi help to expand upon characters and their relationships while also building up good chemistry between each girl and Raku.
Another thing to mention here is that Nisekoi doesn't rely on using naked women or ecchi situations to keep its reader's attention. Rather, it relies more on making the reader understand each character and their motivations, and couples that with a lot of comedy to boot. So in this way, it moves out of the rankings of just harem manga and can be considered a decent story in a more general sense.
When you talk about characters in a harem manga, a lot of it comes down to preference. Some people really enjoy certain tropes while others hate them, and I happen to be the type of person to like the characters in Nisekoi. I actually enjoy almost every character introduced in terms of personality or story. Even the side characters have flavor and their own arcs dedicated to them. Yes it is true that they are not the most rounded or deep characters, and that they don't change a ton throughout the story, but I'd argue that its excusable since the harem genre really doesn't need them to be. They're just so much better than all the characters in other harems though, since they do have history and a bit of depth to them. If you don't like tsunderes though, I would suggest you not read this.
Art-wise I actually quite like the style. A lot of the character designs are fairly memorable and the quality of the drawing is pretty consistently good throughout. Personally, I also really like the style of comedy where characters' faces are drawn more in detail or are really over-exaggerated, so seeing that in this manga is a plus.
That being said, there are still a few downsides to Nisekoi. The first is that there are a decent amount of fluff chapters that don't add too much to the story, but rather are there to just pad the time. Also, the sheer amount of people getting interrupted when they are about to confess is also something that gets annoying at times, but it's a necessarily evil for harem manga honestly. There is also a lot of missed opportunities to use the character's relations to the mafia, yakuza, police force, etc to make more interesting situations for the characters to experience. Sometimes, the switch between slice of life and progressing the plot was a bit forced too, but it's honestly not too bad of a problem.
Overall, Nisekoi was a really enjoyable read. Though it's not one of those 'analytical' reads that you can break down and say what's good about it and whatnot, the amount of fun you can have while reading it more than makes up for that. You're given reasons to care about the characters, the chemistry between them is shown well, and the story doesn't rely on naked girls to gather a following. Just when I was beginning to believe there was no good harem manga out there, I found Nisekoi and it gave me hope for a dying genre. Of course, a lot of your opinions on a harem are gonna be based off of who you like and dislike, but I think Nisekoi shows its worth as a competent story above all of that.
