The characters make you want to read on

Belly's life is measured by the summers she spends at the beach house, where Susannah stays with her sons Conrad and Jeremiah stay. All year long Belly counts down till she goes to stay with her mother and brother. It is like they are one family and Belly grows up feeling she has two extra brothers.
But the summer she turns sixteen, she is more grown up than ever and everything seems to change for her. At this point in the story you can feel that everyone noticed Belly being on the point where she is still a kid, but also not anymore. And it increases the intensity between her and the boys. Belly starts to explore.
The storyline isn't very strong, but what makes you want to read more are the characters. A group of people with a bond so strong, on their own they are individuals all different. But when Belly turns sixteen, they all deal with it their own way.
I am curious about the sequel because the end was both so abrupt and interesting at the same time.