From Viz:

Risa Koizumi is the tallest girl in class, and the last thing she wants is the humiliation of standing next to Atsushi Otani, the shortest guy. Fate and the whole school have other ideas, and the two find themselves cast as the unwilling stars of a bizarre romantic comedy duo.

Lovely Complex Plus is actually volume 17 with the final chapter called Love Com Final. The first two chapters are about before Koizumi Risa and Otani Atsushi met each other. The third chapter is about their first encounter and a little bit of what happens to them after the ending of Lovely Complex.

*Contains a side story called Hoshi ni Natte mo Aishiteru (Even When I Become A Star, I'll Still Love You) in vol 12:
Reina wakes up surprisingly in her boyfriend's room. But it seems that she passed away three days ago...

In 2004 Lovely Complex received the 49th Shogakukan Manga Award for shōjo.