I see this book as being a long writing exercise on the subject of death and sex (will Freud ever get uncool?), mainly because the author made sure we see both of these themes in the character's lives. And only these two themes.
As any writing exercise you sometimes come across an epiphany that actually makes sense and this is what kept me going but, overall, I was very disappointed with the simplicity of this book. Everything was about death and about sex in ways incestuously connected. It seemed like the meditation of a teenager faced with tragedy but still raging with hormones.
The pieces concerning death were (obviously) better written and more carefully prepared whereas the subject of sex was very trivially portrayed and it ruined the atmosphere of the book, frankly. The book gives you the impression of a heavy dream, touching all of those painful experiences that you don't want to think about mixed with the even sadder experience of unfulfilled sex (unfulfilled for the girls; Toru was always having fun).
Now, I do have a problem with the obvious masculine view of things (which Murakami never fails to deliver) but that's just the reality, we can't expect all male writers to be capable of assuming a valid feminine point of view and some writers, even when they're sexist, can deliver a perspective that is of importance in a book.
There are countless Toru Watanabes in the world and this is how they think, we still need to know that even if it's uncomfortable.