This answer contains spoilers… (view spoiler)[We knew from the beginning that Lydia was dead, and I thought that the whole idea of a young life ending too soon was very sad. We're made to believe that Lydia's life was so horrible, because of her painful interactions with classmates and family, that she felt suicide was preferable to continuing in this life. But, then we find out that the time alone in the boat on her last night gave Lydia a chance to reflect on things, and realize she had the power to change her life for the better. All she had to do was to stand up to everyone who had taken advantage of her, and finally say no - no more. I didn't feel as sad anymore when she accidentally slipped and fell into the water, because I knew she was happy and at peace. I actually felt kind of sad for the people who never got to meet this Lydia with the new attitude. They would have learned how to live their own lives without using her as a crutch. She would have made them become better people sooner as a result. However, Lydia did unintentionally leave clues for those closest to her including the cookbook that her mother found, the memories her dad shared with Hannah, the information Hannah and the neighbor shared with Nate.
Helen I also found the book sad. There was no happy ending. Everything was open ended, How did the relationship progress between James and Marilyn?. Did Nath continue at Harvard? We will never know. yes, I felt troubled when I finished reading.
This answer contains spoilers… (view spoiler)[- I Don’t Think it was Sad I Think It had A Happy Ending. Think About It At The Beginnings everyone Lives Is Spinning Out Of control And Then At The End Everybody Got What They wanted And Needed Closer. The Siblings Finally Got Some Attention, Because All They Cared About Was Lydia (hide spoiler)]
Trudy Walter Carlson
This answer contains spoilers… (view spoiler)[Very very sad and depressing. I'm assuming that James and Marilyn repaired their marriage because they were reaching out to one another, and the comment regarding Nathan viewing the world from space indicated that he eventually did become an astronaut. (hide spoiler)]
This answer contains spoilers… (view spoiler)[It was sad because these dysfunctional parents scarred their children for life. None of them succeeded in anything due to parental guidance, but only thought their ability to rise above the nightmare dynamics in the family. The idea that they could all miraculously turn their lives around and move happily forward made for a weak ending. (hide spoiler)]