First of all, the main story is about a student falling in love with a teacher. It tells about the struggles of their relationships since the teacher has to enforce his being a teacher and care about the student's future as well as keep said relationship a secret since the child's underage.
Personally, Ano Kado Wo Magatta Tokoro has a bit more deeper sense and maturity compared to Boku wa Bokunari ni. But if you squealed for one, then read the other as it's definitely worth it. :)