I initially watched the anime on recommendation from a friend, and I quite enjoyed it, and like most fans, found the ending to be confusing and quite disappointing. So, I turned to the manga.
Kare Kano is one of those stories that you can easily relate to. It has characters living out their everyday lives, and the circumstances that they find themselves in, you can easily imagine them happening to yourself.
The manga covers a WHOLE lot more story than the anime. The anime only covers the first 7 volumes of the manga (It ends at the beginning of the Culture Festival). There are 21 volumes in this series, so lets face it, if you've only seen the anime, you've only seen a fraction of this wonderful series.
At the heart of this story is the romance between Yukino Miyazawa and Soichiro Arima. Yukino is an honors student, and the envy of her classmates and appears to be the perfect model student, but this is just a facade that she puts on because she loves to be praised and is a self proclaimed "Queen of Vanity". When she starts high school, she is shocked that someone else beat her entrance exam score and became the class representative, that person being Arima.
This spawns a rivalry (at least in Yukino's perspective) between the two, and its during this time that Arima discovers that the Yukino at school is just a front, and to keep him quiet, he makes Yukino his slave. They become friends, and eventually, Arima confesses his feelings for Yukino to her, and they begin dating.
The story has a fairly large cast of characters, and throughout the story, they all get their time in the spot light, and the manga covers subjects like bullying and peer pressure, academic stress, complex family issues like child abuse and abandonment, marrying young and unexpected pregnancies.
This is one of my favorite romance manga's, right along with Love Hina, Ai Yori Aoshi, and MARS. The story is captivating, immersive, and extremely well executed. If you're a fan of the genre, then I highly recommend this as a must read.