Reckless

Reckless by Lauren Roberts

The book starts out with the two lovers hating each other because each has killed the other's father. It ends with them reconciling, but with his brother proposing marriage to her. In there the middle, there is non-stop Hollywood-style adventure. He chases her and after various escapes finally catches her. Then she is rescued and he is caught. Then they are both caught. They run through escapes and "play lovers" a few time before realizing they do love each other. They find out more about their past and the societal plans. Finally they reach his brother who is now the ruler. There are plenty of twists and turns that are just plausible enough to work, with the relationship gradually growing in a believable fashion. The world building remains a little confusing, but is not super important.