Ravinder "Ravi" Mcleod is training to be an officer on a generation ship going from Earth to Tau Ceti. While not strictly speaking a heredity based society, officers tend to be children of officers & crew tend to be children of crew. The ship (one of three in a fleet) is coming up on Braking Day, the point in the trip where the ship flips around, then fires its engines to begin decelerating. A.k.a., Braking Day from the title.

There's lots of plain drama just from keeping a ship in good shape and heading toward its destination. There's lots of drama because of the hierarchical society that dominates the ship. And there's lot of drama because Ravi starts seeing visions of a girl whose only words Ravi can understand are "help us".

This is a very young adult themed book, though I don't know if it was officially marketed as such. All the spotlight characters are coming of age. Pretty much anything an adult does is either off screen, or an authority figure in opposition to Ravi and his friends. As such, don't expect much in the way of adult motivations.