Boku to Kimi to de Niji ni Naru isn't your typical shoujo in the sense that the main character isn't some disgustingly annoying, doubtful girl whose world revolves around love. Boku (I'm too lazy to write the entire name again, so bear with me), is more about friendship. There is love in the story, yes, but it develops slowly.
It's very, very similar to Kimi ni Todoke.
Toudou is a tsundere. She's candid, which causes other girls in her class to hate her. Toudoulives on a strict schedule and wants to have an arranged marriage in the future -- for good reason, too. Her
father's a whimsical man who randomly quit his job to study udon. Her sister fell in love with a pilot who's going to Costa Rica. Just about the only "sane" person in Toudou's family is, well, her.
Toudou isn't your typical "Wahh? Does he like me?" or "Ahhh~ What can this mean?!" character. This is, I believe, what sets Boku apart from the other shoujo (and Kimi ni Todoke).
I recommend this manga to those who're more interested in reading about friendship. There are also some good life advice in Boku (i.e importance of youth, living spontaneously, etc.) so if you're tired of reading about handsome heart-throbs and painful love stories, then give this a shot.