This is my all time favorite book. I've read it probably six or seven times. The story is told over a succession of 20 summers. What I have always loved about this story is that Hirschfeld creates and manages the lives of a number of great characters and orchestrates their interactions with each other in such a realistic, stark, believeable way.
Through each summer you see the dynamic change between people and watch how their lives unfold, with everything revolving around the summers they spend on Fire Island.
This book is very hard to find, but it's a gem and one I highly recommend.